Why are some rooms warmer than others with radiant baseboard heat?
Most hot water baseboard is not radiant to any significant extent - it's a convector (air heater) and most can be adjusted to flow more or less air (resulting in more or less heat) by adjusting "flaps" on the baseboard shell. They can also (especially old setups in place for a long time) be impacted by buildups of hair, lint, dirt, dust-bunnies etc. that block the flow of air, so opening up the shell and vacuuming and/or blowing out decades of detritus can make a big difference.

An article from the Bangor Daily News...