Abstract Knowing what problems to expect in an IS planning exercise enhances the probability of a successful outcome. This study identifies the major IS planning problems associated with the three phases of IS planning: the launching phase, the plan development phase, and the implementation phase. Data were collected using a questionnaire survey mailed to senior IS executives in 600 firms. Of the 175 responses received, 138 responses (comprising firms practising IS planning) were used for data analysis. In all the three phases, failing to secure top management support for the IS planning effort is the most serious problem. Not having free communication flow, and not being able to obtain sufficiently qualified personnel are the other two major problems in the planning phase. In the plan development phase, respondents reported ignoring business goals and failing to translate these goals/strategies into action plans as major problems as well. Neglecting to adjust the IS plan to reflect major environmental changes is the other major problem in the implementation phase. Probable explanations were provided for these and other problems.