My 19-month-old daughter has been intermittently resistant to diaper changes pretty much since she could sit up. Basically, once she was able to do that she just wasn't wild about being laid on her back (for diapers or anything else). Here's my recommendations: Try to make the diaper changes interactive, something you do together rather than something you do TO him. Give him a bit of warning that you're going to change his diaper in a minute. Describe what you're doing and why ("I'm going to wipe the poop off now so that you won't get a rash...we're going to put a clean, dry diaper on you and it will be much more comfortable"). Maybe involve him by letting him put the used diaper in the diaper pail (then you can both wash your hands and begin instilling that habit for later), or when he's a bit older letting him help to fasten the tabs on the diaper. Try making up a song to change by (e.g., to the tune of row row row your boat, "wipe, wipe, wipe the poop, wipe the poopy off" or whatever absurd lyrics you can think up on the spot). Finally, something that usually works for us, change the location of where you do the diaper change. For some reason, my daughter often fights the change if it's on her diaper table, but if we use the livngroom rug or the picnic table outside, she's okay with it. Hope this is helpful! Good luck.