Question about smoking tobacco?

As everyone knows smoking is bad for health, but I have a weird question about the habit. Is it the amount that you smoke or how many times you light up a cigarette that's worse? What I mean is that, I know a lot of people who just like to light up a cigarette, have two, maybe theree puffs and then put it out - as opposed to those who light up a cigarette and smoke the whole thing to the filter.