The strategic value of information systems (IS) and the impact of information technology (IT) on business competitiveness has increased the need for effective strategic information systems planning (SISP). However, numerous strategic information systems planning methodologies stress the rational and formal aspects of organizational life, while ignoring the complexity of actual organizational situations which are characterized by human behaviour. Additionally, although numerous researchers have conducted empirical studies examining the relationship between various factors and strategic IS planning effectiveness, many factors have received little attention. This study uses structural equation modeling (SEM) to analyse the effects of organizational context and inter-group behaviour on the success of SISP. A survey of senior IS executives in Taiwan was used to test the relationships between the constructs in the research model. The results showed that certain factors relating to organizational context and inter-group behaviour influenced the success of SISP. Finally, the implications of this finding for IS practice and future research are examined.