As others have said, this isn't necessarily a bad thing. However, I've had a few cases where I created a page for a specific purpose, and then a different page ranked for that keyword term.
When I looked into why this happened, I discovered that within the domain I had links pointing to those unintended pages that used the keyword in the anchor text. Apparently this confused Google. So I changed the anchor text in those links, making sure that the keywords where no where in them. Within a week or so those unintended pages stopped ranking, and then the intended page ranked instead.
I don't know if this is relevant to your situation, but perhaps it will be helpful to someone.