This paper examines the motivation and impact of corporate diversification in Chinese listed firms. We find that in local government owned-firms there is a non-linear relationship between the level of firm diversification and state ownership. As state ownership increases from zero, the level of diversification decreases. After state ownership reaches a certain level, the level of diversification increases as state ownership increases. There is no evidence that ownership is related to corporate diversification in non-state-owned firms or central government-owned firms. We also document that diversification is negatively related to firm performance in local government-owned firms. However, there is no evidence that diversification is negatively related to the firm performance in non-state-owned firms or central government-owned firms. Our findings suggest that agency problems are responsible for local government owned-firms taking value-reducing diversification strategies.