You are right to be worried if your boyfriend is hanging out with the wrong type of person. The likelihood of young men smoking, drinking and taking drugs increases if a friend is already involved in this sort of lifestyle. You can influence and encourage your boyfriend to make better choices, but ultimately it is up to him who he hangs out with. If your boyfriend isn't willing to prioritize you or make healthy decisions, you may decide you need to move on.

Approach Him With Your Concerns

It's your right to express your needs in a relationship, so tell your boyfriend how concerned you are about this friendship and the possibility of him getting into trouble. Pick a time when you'll be alone with him, with no outside distractions. Turn off your phone, and ask him to sit down with you. If you feel upset when trying to talk, regroup by taking a deep breath and counting slowly to 10, advises Preston Ni, Professor of Communication Studies at Foothill College, in an article on "Psychology Today."

Be Clear on the Consequences

Young guys see the benefits of risky decisions more clearly than the costs, suggests a study by psychologists at Temple University, which was published in "Developmental Psychology" in 2005. Make it very clear to your boyfriend what he stands to lose by hanging out with a troublemaker. Start your statements with "I" to make him more receptive. Say, for instance: "I worry that hanging out with Rob will get you into trouble. I feel devastated at the thought of you ending up in serious trouble, and me losing you because of that."

Have More Fun Together

Partners can have an important influence on their boyfriends' choices, so you may be able to tempt your guy away from trouble. Young people naturally tend to like taking risks, so plan some exciting dates where he can feel the thrill, but not get harmed. Riding a roller-coaster, going to a water park or rock climbing together can give you both a major buzz. When your boyfriend sees how much fun he can have with you, he'll be less likely to want to hang out with anyone antisocial.

Introduce Him to New People

If troublesome friends can be a bad influence, good friends can have a positive impact, too. Introduce your boyfriend to some nice people you know who share some of the same interests as him. If you can't think of anyone suitable, develop a new circle of caring friends together. Find positive, healthy people to befriend within your community, in places such as a church, the gym, meditation classes or volunteer committees at your school.