A sport boot, such as a snow ski boot, that includes a shell having a rigid foot portion. The foot portion includes a heel pocket and an instep region that is largely immovable relative to the heel pocket due to the rigidity of the foot portion. The boot also includes a highback support region that snugly engages the leg of a user during use. A heel-track is located on the dorsal side of the boot between the highback support region and the heel pocket. The heel-track provides a concave space that receives the user's heel when the user is putting-on and taking-off the boot to counter the relative immovability of the instep region of the boot against the engaging action of the user's foot. The sport boot can also include a special boot liner having an expandable dorsal region, and, optionally, other features that compliment the heel-track of the shell.