I had trouble with mice in my garage a winter ago and we have trouble with them in some of our logger shacks out in the wild. One thing that has always worked are these:
http://www.canadiantire.ca/en/pdp/vi...3847p.html#srp
Since I put these up I have caught a few but I think they were just the stragglers, both in my garage and out at our huts. This winter I didn't see a single mouse on the traps nor a piece of mouse crap in my garage, it helps to keep things up off the floor as well obviously.
With our huts out in the bush it took a while but now on our bi weekly visits we don't see any mice on the traps. Before it was 3-4 a visit. I never thought something like this would work, but in my case it has.