From 20 Questions for Leaders:
Which is most important to your organization—mission, core values or vision?
In my humble opinion Core Values are the most important for any organisation. Once you have these, then aligning Vision and Mission are fairly straight forward.
However, if you don’t really know what your Core Values are, then you can’t align the Vision and Mission with them, and anything which is not aligned to Core Values will fail.
Our Core Values are what drive us, they are aspirational and when our aspirations are not being satisfied, then we don’t give our best efforts.
Which of them is most important to you, or your organisation?