text: The Real Madrid forward got the decisive goal when he stooped low to head in Miguel Veloso's superb cross.
  Up until then they were frustrated by a disciplined Sweden side, who went close through Johan Elmander, Sebastian Larsson and Kim Kallstrom.
  No player has scored more headed goals (four) than Ronaldo in European World Cup 2014 qualification
  The second leg will take place at Solna's Friends Arena on Tuesday.
  That promises to be another fascinating contest between two sides, with the impetus now on Sweden to attack, having set their stall out to defend for long periods during the first leg.
  They did, however, create the better chances in the opening 45 minutes despite Portugal enjoying 67% of the possession.
  With Paris St-Germain forward Zlatan Ibrahimovic given special attention by Portugal's defence, his attack-minded team-mates found themselves with more space than they should have been afforded.
  Norwich's on-loan forward Elmander was first to cause nerves in the home support when he stretched to send Mikael Lustig's right-wing cross inches past the post.
  Erik Hamren's men then created two great chances in the space of two minutes. Sunderland's Larsson surged forward from midfield to strike a low shot that Rui Patricio dived to his left to divert, before Kallstrom, winning his 107th cap, smashed an 18-yard free-kick that brushed Portugal's upright.
  Ibrahimovic failed to register a single touch in the opposite box against Portugal
  The home side's best chance of the half came in the first five minutes when Ronaldo and Raul Meireles combined before feeding Joao Moutinho, who drifted round keeper Andreas Isaksson before firing into the side-netting.
  Portugal's frustrations continued after the break as Sweden sat deeper, while their coach Paulo Bento probably would have been left exasperated by some of the awful attempted deliveries into the area.
  But with eight minutes left one cross led to something greater when Dynamo Kiev's Veloso's fantastic delivery found Ronaldo, who threw himself at the ball to give Portugal the lead.
  Moments later, the Real Madrid marksman almost scored his 30th of the season, but saw his header bounce back off the crossbar.
  Sweden offered little as an attacking threat after the break, with Ibrahimovic failing to trouble Patricio and his defence. The skipper will have to show the sort of form he has produced for Paris St-Germain this season on Tuesday if Sweden are to stand a chance of going to Brazil.
  "We would have been very happy with a draw," Sweden coach Erik Hamren said.
  "We played a good game defensively - the goal was unnecessary, we were careless with that cross."
  Bento added: "We created a great early chance and Sweden hit back. But in the second half it was one way for us.
  "It was an important step to reach the World Cup but not yet decisive."
  Match ends, Portugal 1, Sweden 0.
  Second Half ends, Portugal 1, Sweden 0.
  Offside, Sweden. Sebastian Larsson tries a through ball, but Alexander Gerndt is caught offside.
  Attempt missed. Cristiano Ronaldo (Portugal) right footed shot from outside the box is high and wide to the right. Assisted by João Moutinho.
  Pepe (Portugal) wins a free kick in the defensive half.
  Foul by Zlatan Ibrahimovic (Sweden).
  Substitution, Sweden. Alexander Gerndt replaces Johan Elmander.
  Foul by Cristiano Ronaldo (Portugal).
  Pontus Wernbloom (Sweden) wins a free kick in the defensive half.
  Corner,  Portugal. Conceded by Martin Olsson.
  Attempt missed. Josué (Portugal) left footed shot from outside the box misses to the left.
  Cristiano Ronaldo (Portugal) hits the bar with a header from very close range. Assisted by Hugo Almeida with a cross.
  Offside, Sweden. Pontus Wernbloom tries a through ball, but Zlatan Ibrahimovic is caught offside.
  Goal!  Portugal 1, Sweden 0. Cristiano Ronaldo (Portugal) header from very close range to the bottom right corner. Assisted by Miguel Veloso with a cross.
  Corner,  Portugal. Conceded by Anders Svensson.
  Attempt blocked. Nani (Portugal) right footed shot from the left side of the box is blocked.
  Corner,  Sweden. Conceded by Nani.
  Corner,  Sweden. Conceded by Miguel Veloso.
  Substitution, Portugal. Josué replaces Raul Meireles.
  Delay over. They are ready to continue.
  Substitution, Sweden. Anders Svensson replaces Kim Källström.
  Johan Elmander (Sweden) is shown the yellow card.
  Delay in match Andreas Isaksson (Sweden) because of an injury.
  Cristiano Ronaldo (Portugal) is shown the yellow card for a bad foul.
  Foul by Cristiano Ronaldo (Portugal).
  Andreas Isaksson (Sweden) wins a free kick in the defensive half.
  Offside, Portugal. Raul Meireles tries a through ball, but Cristiano Ronaldo is caught offside.
  Attempt missed. Raul Meireles (Portugal) right footed shot from outside the box misses to the left following a set piece situation.
  João Pereira (Portugal) wins a free kick on the right wing.
  Foul by Pontus Wernbloom (Sweden).
  Attempt blocked. Cristiano Ronaldo (Portugal) right footed shot from a difficult angle on the left is blocked. Assisted by João Moutinho.
  Substitution, Sweden. Pontus Wernbloom replaces Rasmus Elm.
  Sebastian Larsson (Sweden) is shown the yellow card for a bad foul.
  Fábio Coentrão (Portugal) wins a free kick on the left wing.
  Foul by Sebastian Larsson (Sweden).
  Attempt saved. Nani (Portugal) left footed shot from outside the box is saved in the bottom right corner. Assisted by João Pereira.
  Foul by Bruno Alves (Portugal).
  Rasmus Elm (Sweden) wins a free kick in the defensive half.
  Corner,  Portugal. Conceded by Per Nilsson.
  Substitution, Portugal. Hugo Almeida replaces Helder Postiga.
target: Cristiano Ronaldo broke Sweden's resistance late in the game to give Portugal the advantage in their World Cup play-off tie in Lisbon.