OBJECTIVES: We examined adolescents' emotional reactions to parental cancer and explored relationships between emotional reactions and adolescents' emotional/behavioral problems. METHODS: Two studies were performed: retrospective and prospective. A total of 221 adolescents (105 sons) of 138 patients (retrospective) and 70 adolescents (31 sons) of 70 patients (prospective) participated. Adolescents reported on cancer-specific uncertainty, loneliness, helplessness and positive emotions (Situation-Specific Emotional Reactions Questionnaire), and filled in the Youth Self-Report once retrospectively during the period of 1-5 year(s) after diagnosis and three times prospectively during the first year (4 months post-diagnosis, 6 and 12 months after T1). RESULTS: Emotional reactions were similar between pro- and retrospective studies. Prospectively, uncertainty and helplessness decreased over time. Uncertainty and loneliness related significantly to adolescents' dysfunction (prospective and retrospective). Relationships between emotions and functioning were stronger and more often significant for daughters. Prospectively, adolescents' post-diagnosis emotional reactions were largely unrelated to later functioning. CONCLUSIONS: Uncertainty and loneliness related to adolescents' emotional and behavioral problems. Daughters' emotions seem more strongly related to functioning than sons'