It's hard to say without seeing the recipe, but it could be a couple of things.
It could be that there is too much dry ingredients (like flour) and not enough fat (like butter or oil). Try either less flour or more butter/oil or both and see what happens.
If they cookie dough gets rolled into a ball then baked, it could be that you're rolling the balls too big. Try smaller balls, or flattening them a bit. If they cook from slices, then maybe you're cutting the dough too thick. Try thinner slices.
It could also be the oven temperature needs to be adjusted or maybe they need to cook longer.
Some other troubleshooting help is on this page:
http://www.goodhousekeeping.com/recipes/cooking-tips/solve-cookie-problems
Answered Feb 18, 2012
Edited Feb 18, 2012