Strategic information system planning (SISP) has been identified as a critical management issue. It is considered by many as the best mechanism for assuring that IT activities are congruent with those of the rest of the organization and its evolving needs. Our research investigated the success of SISP as a function of its key success factors (KSFs) in different contexts and SISP approaches, in a framework that integrated all of the SISP components and provided a new perspective on how the constructs are instrumental to produce SISP success. Based on responses from 172 American CIOs, our study’s findings empirically supported our research model: the combination of SISP context and approach was found to have a moderating influence on the basic relationship between SISP KSFs and its success, the best predictor for the long-term success of the SISP process was apparently based on the three-way interactions between SISP’s KSFs, its approach and its context. In addition, specific combinations of SISP approach and SISP context were found to decrease or increase the size of the ‘‘planning paradox’’ (the inconsistency in the behavior of the ‘‘basic relationship’’ between the three).