Resveratrol belongs to the large group of biologically active substances found in plants. This compound is classified as phytoestrogen because of its ability to interact with estrogen receptor. Numerous beneficial effects of resveratrol described in the literature involve cardioprotective, anti-cancer, anti-inflammatory and antioxidant action. Recently, this broad spectrum of effects is enlarged by new data demonstrating a great potency of this compound in relation to obesity and diabetes. It is well established that resveratrol exerts beneficial effects in rodents fed a high-calorie diet. In some studies, resveratrol was reported to reduce body weight and adiposity in obese animals. The action of this compound involves favourable changes in gene expressions and in enzyme activities. The accumulating evidence also indicates the benefits of resveratrol in diabetes and diabetic complications. It is known that resveratrol affects insulin secretion and blood insulin concentration. In animals with hyperinsulinemia, resveratrol was found to reduce blood insulin. Moreover, numerous data indicate that in diabetic rats, resveratrol is able to reduce hyperglycemia. The mechanism of resveratrol's action is complex and is demonstrated to involve both insulin-dependent and insulin-independent effects. These data point to the potential possibility of use of resveratrol in preventing and/or treating both obesity and diabetes.