yes - try using the save for web option
you can then choose to use a png-8 or png 24
png24s are larger but give much better results when using alpha/opactity on an image
if the image is solid or what the image is being placed on is going to be solid then a png 8 is better as you have a finer degree of control over the quality & ultimatly the size of the file - have a play around i recommend using the 2 screen option so you can see the orignal image and compair it to the one you optimize
bit more info here http://www.tutorial9.net/tutorials/photoshop-tutorials/saving-images-for-the-web/