Prior research shows that family firms are generally less likely to diversify, but it remains unclear which mode of diversification in terms of internal versus external diversification family firms are more likely to choose once they decide to diversify. Similarly, it is unclear which type of diversification in terms of product versus international diversification family firms are more likely to focus on in comparison to nonfamily firms. Based on insights drawn from the goals, governance, and resources framework, this dissertation investigates the modes/types of diversification in family and nonfamily firms, as well as among various types of family firms. Specifically, I propose that family firms will prefer internal to external diversification to a larger extent than nonfamily firms. I further propose the strength of preference for internal to external diversification is likely to vary among different types of family firms manifested in the level of family ownership, family participation in the top management team and board, and generation of family members owning and controlling the family firm. Likewise, I theorize that family firms would prefer product to international diversification to a larger extent than nonfamily firms and that the strength of preference for product diversification is likely to vary among different types of family firms. A sample of 573 firms drawn from the S&P 1500 index was used toexamine the difference between family and nonfamily firms, and 136 family firms to test the heterogeneity hypotheses. No significant differences were found between family and nonfamily firms in their relative choice on internal over external diversification (Essay 1) and product over international diversification(Essay 2). Consistent with my prediction, I found family representation in the top management team has a significantly positive effect on a firm's tendency to engage in product rather than international diversification. However, in both Essay1 and Essay 2,I did not find significant effects of the other heterogeneous variables on a family firm's tendency to engage in one mode/type of diversification over the other. A rationale for these non-significant relationships is provided. Contributions and implications of this study are also discussed.