This paper examines the effect of family business and managerial optimism on the investment-cash flow sensitivity. We divide the CEOs in family businesses into family member CEOs and professional CEOs and then investigate whether these two types of CEOs and the third type-CEOs in non-family firms-have different influences on the investment-cash flow sensitivity. The results show that optimistic family businesses, compared with optimistic non-family businesses, have higher investment-cash flow sensitivity and the higher investment-cash flow sensitivity mainly results from optimistic family member CEOs. Finally, we find that this higher investment-cash flow sensitivity is due to overinvestment rather than underinvestment problem.