Every week BBC Radio 1 plays a countdown of the week's top songs, based on downloads and online streaming.
In May, the programme will move from Sunday to Friday evenings.
CBBC will also launch a TV version of the Official Chart Show, presented by Cel Spellman.
The new programme will be broadcast live from the Radio 1 studios and presented by Greg James and will play the top 20 songs of the week.
The Official Chart Show is being moved from Sunday to Friday evenings, as part of a big shake-up of the music charts.