Although I have been smoking on some occasions in the past, I decided to tell my parents about my chronice use once I started to use it regulary. I figured they will find out one way or another, so I decided to put faith in my own hands and just go ahead and tell them.
Now, before I continue, the fact that I'm 18, and an exellent student must be kept in mind. I decided to tell them the day midtearm report cards came. With an 88% average I couldn't go wrong. Also, my brother, who is older than me, has been a vocal chronic user and my parents did not care about that at all. Anyway, when I did tell them, their response was that I'm 18 and that they couldn't stop me from doing it even if they wanted to (very true), and that I should just use it resposibly.

So basically what I'm trying to say is that certain prerequisites are required, if yor parents are the "caring" type. You should be decent at school minimum, and you have to be relatively well behaved. Because if you are not, chances are they will start blaming poor 'ol Mary Jane for yer problems, and start hating you for it.