How is it easy to screw things up? You specify the version of a dependency when you write each POM file. If there are two projects, each with different dependency versions, they only get the dependency version they requested. Only if you have two different dependencies that report themselves as having the same Maven coordinate, that is to say the same Group Id, Artifact Id, and Version number, will you have any problems. But then that isn't a "Maven" problem insomuch as it is a bad dependency.