During the last decades a considerable amount of research has been focused on cancer. Recently, tumor cell metabolism has been considered as a possible target for cancer therapy. It is widely accepted that tumors display enhanced glycolytic activity and impaired oxidative phosphorylation (Warburg effect). Therefore, it seems reasonable that disruption of glycolysis might be a promising candidate for specific anti-cancer therapy. Nevertheless, the concept of aerobic glycolysis as the paradigm of tumor cell metabolism has been challenged, as some tumor cells exhibit high rates of oxidative phosphorylation. Mitochondrial physiology in cancer cells is linked to the Warburg effect. Besides, its central role in apoptosis makes this organelle a promising “dual hit target” to selectively eliminate tumor cells. From a metabolic point of view, the fermenting yeast Saccharomyces cerevisiae and tumor cells share several features. In this paper we will review these common metabolic properties as well as the possible origins of the Crabtree and Warburg effects.