Parent training programs (PT) have consistently been shown to be effective for families with children displaying disruptive behavior problems (DBP). However, not all families seem to benefit equally from these programs and the effects are small to moderate. Several studies have examined single factors that might explain variations in outcomes with inconclusive results, and there seems to be a need for a deeper understanding of complex pattern of factors. This generally requires large sample sizes which might be difficult to obtain. Qualitative comparative analysis (QCA) is a method, rarely used in mental health research, that originally was developed for use in research with small and medium sample sizes for understanding and exploring complex real-world situations. The aim of this study was to generate a deeper understanding about combinations of factors that may have an impact on the outcome of PT programs. In addition, we also wanted to introduce QCA in research on mental health interventions and to explore the usefulness of QCA as a bridge between the quantitative and qualitative phases in an explanatory sequential mixed methods study. There were three different pathways, with unique combinations, showing different ways to maintain DBPs after PT and four different combinations of conditions associated with a positive outcome after PT. We also found that QCA was well suited for this type of analysis and that it might be a useful method to generate specific hypothesis that can be tested in future research.