The era of genome-wide association studies has revolutionized the search for genetic susceptibility loci in complex genetic conditions such as psoriasis. There are currently 16 loci with confirmed evidence for association with psoriasis susceptibility but there is the potential for more to be discovered as the genetic heritability of the disease has not yet been fully explained. Many of the associated loci overlap with those for psoriatic arthritis. In contrast to psoriasis susceptibility, few studies have been performed to identify predictors of drug response in psoriasis. As large-scale collaborations and registries for psoriasis and psoriatic arthritis are established, it is likely that a genome-wide approach may be used as a more effective method of searching for genetic predictors of treatment response. However, candidate gene studies will still have a role; for example, it is likely that some disease susceptibility genes will also be markers of treatment response, based on evidence from other diseases. This review summarizes recent advances in investigating the role genetics plays in psoriasis susceptibility and contrasts these to advances made in psoriatic arthritis. Further, it describes the genetics of treatment response in the two diseases and indicates how susceptibility loci could be used to identify drug response in the future.