What kind of memory for iMac G5?

Hi, I have an iMac g5 2.4 GHz intel core 2 duo model iMac8,1. I still have the original 1 GB of memory and and am running slow for some applications. Want to upgrade memory but not sure what kind to buy? Does anyone know?

Welcome to Mac-Forums!

200-pin PC2-6400 (800MHz) DDR2 SO-DIMM is the right RAM for your iMac (source: Mactracker).

Brand? Best place to buy RAM for Mac is OWC Performance Upgrades; FireWire USB SATA Storage; Memory, more at OWC. Various brands are thoroughly tested by them for Mac compatibility.

Others have bought and recommended Crucial or Kingston brand. The RAM in my eMac, which I bought from OWC, is Hynix brand.

Thank you ever so much! Should I buy two 2GBs and get rid of the 1GB that's in there, or leave the 1GB and just buy a 2GB for the other slot?

What you query is what I'd do in your situation, ie. 2 x 2 Gb. You do have the option of 3 Gb, because you don't need matched pairs, but I believe firmly on the old maxim "you can never have too much RAM!"