The range of any CB is affected by what is between you and the person you want to speak to. This particularly applies to hand-held CB's as they have much smaller aerials, so the performance will be that much less.
As a general idea to range...
Hand-held to hand-held in open countryside ½ to 1½ mile, less in wooded or built-up areas.
Hand-held to vehicle mounted CB approx 1-3 miles.
However... when used inside a vehicle on its own aerial, the range of a hand-held CB is dramatically reduced - down to 40-50 yards ! The only real option for using a hand-held inside the vehicle is with an external aerial, mounted on the outside.
Most of the handheld CB's we sell come complete with a 12v car kit which enables them to be plugged into a cigarette lighter plug for power, and have a connection for external aerial.
When used with a speaker mic like the ones pictured below, they can be just as effective as a conventional fit in the vehicle CB :