This study evaluated the aspects of complex decisions influenced by peers, and components of peer involvement influential to adolescents' risky decisions. Participants (N = 140) aged 13-25 completed the Columbia Card Task (CCT), a risky choice task, isolating deliberation-reliant and affect-reliant decisions while alone, while a friend monitors choices, and while a friend is merely present. There is no condition in which a nonfriend peer is present. Results demonstrated the risk-increasing peer effect occurred in the youngest participants in the cold CCT and middle-late adolescents in the hot CCT, whereas other ages and contexts showed a risk-decreasing peer effect. Mere presence was not sufficient to influence risky behavior. These boundaries in age, decision, and peer involvement constrain prevailing models of adolescent peer influence. [ABSTRACT FROM AUTHOR]