Definitely, longer distance running is great for building up a good cardio base/rehab after a lay off etc but as far as boxing is concerned I'm a believer in shorter higher intensity runs... still a decent distance 4-5 miles but I like to run this at a moderate pace and then go flat out on 3-4 sets of hill sprints I like to do for 4-5 reps each.

The Anaerobic (sprint) energy system is much more important, though they all need to be trained.

Case in point, even when I haven't been running often I ALWAYS have the lungs/wind for it from doing bag work, Plyometric workout, supersets etc

it takes me a short while to get my muscular endurance back up with relation to that particular running motion but there isn't really that much cross over in the adaptations that distance running causes to your leg muscles/nervous system and the movements your legs under go in boxing.

Running is very important to a boxer, hauling yourself on a long slog not so much. It has to be done properly and relative to boxing. You're not going to really train the leg muscles themselves that usefully (you'll obviously get a bit more bounce) but you can train the relative energy systems for well with proper running.

Gonna stop rambling now.