This dissertation studied the behaviour of a large group of individual investors from Robeco, ASN Bank and Triodos Bank. The research shows that sustainable investors also behave more socially in other contexts than common investors. For example, sustainable investors donate substantially more money to charity, practice volunteer work more frequently, and are more often registered as organ donors. Moreover, the dissertation shows that there are two types of sustainable investors. A large group of investors buys sustainable funds because of their personal inclination to contribute to a better world. The other important group of investors buys sustainable funds for a financial reason, such as tax privilege or a higher expected return. And fin...