Considering coping as dynamic process within the family, effects of gender and diagnosis are investigated. Dissimilarity within couples in coping with childhood cancer is studied longitudinally in its effects on quality of life of mothers, fathers, and the sick children. A total of 108 parents out of 54 complete families participated in a prospective study. Twenty-five families had a child newly diagnosed with cancer, 29 families had a child newly diagnosed with juvenile diabetes or epilepsy. The Coping Health Inventory for Parents, the Trier Coping Scales, and the Ulm Quality-of-Life Inventory for Parents were employed 1-2 weeks after diagnosis and again 10-12 weeks after diagnosis. In face of childhood cancer, parents develop more rumination, defense, and information seeking, and less social support seeking strategies compared to the control group. Mothers report more frequent and more effective coping compared with fathers, but mothers and fathers do not differ in their self-reported quality of life. No convergence within couples could be demonstrated in most of the corresponding coping styles. The strongest correlation between mothers and fathers appeared in the religious coping style (r=0.60, p<0.001). Coping dissimilarity within couples in social support seeking and religion is correlated with an improvement of parental quality of life. Parental dissimilarity in information seeking is correlated with a decrease in the child's quality of life. Coping dissimilarities between fathers and mothers have differential effects on the family members. For this reason, psychosocial interventions should support dis-synchrony when it appears adaptive, and they should help parents to overcome those differences that negatively affect their child.