To explore the underlying genetic defects of dilated cardiomyopathy (DCM) we applied OS-Seq technology as a novel comprehensive diagnostic tool. Despite our increasing understanding of the genetics of DCM the genetic basis of the disease is still poorly understood. We were able to identify pathogenic variants in 47.6% of the cases with family history of DCM and in 25.6% without family history using our Pan Cardiomyopathy Panel in the analysis of 145 Finnish DCM patients. Remarkably, 53% of the significant variants found were titin (TTN) truncations. As the link between titin variants and DCM was established only recently, our study adds substantial evidence and highlights the importance of titin variants underlying DCM. Furthermore, this study showed, once again, that targeted, panel-based sequencing enables high diagnostic yields in clinical setting.