There is co-morbid occurrence of adolescent problem behaviors, and these behaviors manifest differently and vary in severity. For instance, some adolescents who suffer from stress and distress become addicted to substance and internet use, whereas some act out in the form of misbehavior and delinquency. In particular, research findings have shown that there are gender differences; with boys tending to employ externalizing and risk-taking behavior as ventilation, while girls tend to internalize stress and become depressed. Nevertheless, different problem behaviors may share similar etiologies. Adopting the ecological approach, adolescents behaviors result from the complex interplay between themselves and the surrounding environment. These issues will be addressed in this book with experience from research from Hong Kong in a Chinese context.