Background and aims: Calmodulin (CaM) is a ubiquitous Ca2+-sensing protein regulating many important cellular processes and playing a crucial role in Ca2+-dependent signaling in all eukaryotic cells. Over the last few years several CaM-associated variants have been identified in a small group of patients of young age with cardiac arrhythmias. CaM plays an important role in the cardiac contraction cycle, among which we find it as an interacting partner with the small-conductance Ca2+-activated K+ (SK) channels. In order to understand the molecular mechanisms underlying the different phenotypes, we here aimed at studying the impact of novel CaM variants on SK3 channels. Methods: For the electrophysiological evaluation, HEK293 cells stably expressing hSK3, were transiently transfected with pXOOM-rCaMWT/variant. Whole-cell patch-clamp recordings were acquired upon application of voltage ramps using a calculated free Ca2+ concentration of 400 nM. For the immunocytochemistry studies MDCK cells were transiently transfected with pXOOM-rSK3WT/variants and were grown to a confluent, polarized state on glass coverslips before they were stained and imaged. Laser scanning confocal microscopy was performed using Zeiss LSM 710 confocal system. Results: Out of the 9 variants evaluated in this study, the variants CaMN54I, CaMD96V, CaMA103V, CaMD130G and CaMF142L significantly suppressed ISK,Ca compared to CaMWT. Further, CaMD129G affected the membrane expression in contrast to CaMN54I, CaMD96V, CaMA103V and CaMF141L which more likely render the SK3 channel non-functional. Conclusion: This study puts forward the suggestion that CaM variants have divers effects on the SK3 channels and are giving rise to various molecular disease mechanisms.