Recently, Green IT has become one of the hottest topics in IS field. Among questions related to Green IT, the first one is “Why organizations adopt Green IT”. Just like there is no consensus on what Green IT is, no consistent answer has been proposed for this question. Beginning with a clarification of the definition of Green IT, this paper reviewed and summarized the predictors of organizational adoption of Green IT identified by previous studies. Based on the TOE framework, a taxonomy was provided in this paper. Several critical observations were discussed as well.