This thesis reports on the association between particular psychological attributes of owner/operators and organisational financial performance in New Zealand small to medium sized enterprises (SME's). The specific psychological attributes of interest are ambiguity tolerance, self efficacy, resilience and planning orientation. A direct response mail survey was sent to 4,500 New Zealand organisations fitting the criteria for this study. Ambiguity tolerance, self efficacy and resilience were assessed using established item scales from the literature. Planning orientation was assessed using planning scenario analysis. Data analysis was conducted using structural equation modeling. Results show that the planning orientation of owner/operators has a significant direct association with organisational financial performance. Ambiguity tolerance, self efficacy and resilience were found to have a significant indirect association with financial performance. The findings of this research have implications for both theory and practice. Theoretically there are implications for cognitive and personality psychology, organisational theory and behaviour, entrepreneurship and research related to the psychological attributes of interest in this thesis. Practically, the results provide managers with a meaningful tool to aid in the selection, training and management of individuals responsible for strategic decision making in SME and other organisational settings.