Well, it does matter if you are interested in it. But if you can produce an excellent extended essay in a field where you know the rules (and dont have to use many outside resources,) then you will have no prroblems. I did my EE in English. Okay so you are Year 1 IB. good you've got lot's of time. However, if there are teachers at your school for computer science and you know you can do it, then do it in Comp Sci. I just say English so you can do it quick, get away with it, and even do a good one, because English is easy to write an essay in. but in other subjects, there are no rules. (Well, not like in english anyway). Don't get me wrong, i detest eng. lit. but it was the easiest essay subject for me to choose, and probably the best essay i've written in my life.