if it is XD and SD..... both are like the VHS and Beetamax thing, compatability maybe slightly different, but all in all they do the same job. only really major difference is the fact that they are different physically to look at and XD is a lot more expensive. If you are looking into buying something with these, go for the SD as they are more common and a lot cheaper. Some articles that may help are http://www.dcresource.com/forums/archive/index.php/t-1336.html http://www.steves-digicams.com/flash_memory.html