BACKGROUND: This study aimed to examine the parental physical illness’ effect on behavioral problems among adolescents, and the effects of being an only child, family cohesion, and family conflict on behavioral problems among adolescents with physically ill parents in Liaoning province, China. METHODS: This cross-sectional study was performed in 2009. A questionnaire including two dimensions of the Family Environment Scale (family cohesion and family conflict), self-reported Strength and Difficulties Questionnaire (SDQ), and demographic factors was distributed to the subjects. RESULTS: Among the 5220 adolescents, 308 adolescents lived with physically ill parents. The adolescents with physically ill parents had more behavioral problems than adolescents with healthy parents. Among the girls who lived in families with physically ill parents, the SDQ score and the prevalence of SDQ syndromes were higher in the girls with siblings than the girls without siblings after adjusting for variables; the effect of family cohesion on SDQ was significant after adjusting for variables. CONCLUSION: Interventions targeting family cohesion may be effective to reduce behavioral problems of adolescents with physically ill parents.