According to the Elaborated Intrusion Theory of Desire, desire thinking and an associated deficit are fundamental factors to the emergence of craving. In the special case of problematic social networking sites (SNS) use, this experienced deficit could be constituted of an online-specific fear of missing out (FoMO). To test the interaction of these cognitions and their influence on problematic SNS use, we tested a serial mediation model on a sample ofN= 193 individuals who use SNS (73% female,Mage= 28.3,SD= 9.29). We found that desire thinking predicted FoMO and both variables were only significant predictors of problematic SNS use when considered in interplay with craving. Ad hoc analyses revealed that the verbal subcomponent of desire thinking is more strongly associated with FoMO than imaginal prefiguration. Our results highlight that neither desire thinking nor FoMO are inherently dysfunctional but become problematic when they increase craving for potentially problematic SNS use.