This started as a recipe from friends, using instant coffee. They insisted that the quality of the final product is not affected by the quality of the vodka used. After switching to fresh coffee and "perfecting" the process, I learned that kahlua is a rum based liqueur. I have yet to make a batch with rum. **Update... September 13, 2006 -- I have made a batch with rum, and find it even smoother than making it with vodka.