I started back up at the gym about a month ago, and am already seeing small gains. Only lifting, no cardio.

Is it possible to do both? I am on a 5 day muscle mass split and I would still like to be able to jog and/or hit the heavy bag throughout the week to increase stamina and lung capacity. I am a heavy smoker (working on quitting) and I definitely feel like I need the stamina boost, but I don't want to jeopardize gaining.