OBJECTIVES Diabetes mellitus is an important public health problem in Mexico. The illness progression is faster when the patient also presents overweight or obesity. The objective of this study was to evaluate the clinical and economical impact of the use of metformine + sibutramine versus metformine and acarbose as a treatment for weight loss in patients with DM-2 with obesity and/or overweight, in Mexico. METHODS Cost-effectiveness analysis by decision tree of the pharmacological treatments for weight loss in patients with diabetes mellitus II from the health service provider perspective, considering a temporary horizon of 5 years. The considered effectiveness measure was the percentage of patients that reaches an IMC ≤ 25 without peritoneal dialysis. Costs were estimated using 2008 prices and are expressed in US dollars (exchange rate of 11.14 pesos/ 1 US dollar). RESULTS According to the model, the effectiveness of each alternative was: metformine, 2.16%; acarbose, 2.16% and metformine + sibutramine 50.18%. The treatement with metformine threw the lowest average cost per treated patient with DM-2 $9,486.3, followed by the treatments with metformine + sibutramine y acarbose with a cost of $10,729.3 y $10,892.0 respectively. The average treatment cost-effectiveness in ascending order is: metformine +sibutramine $21,383.5, metformine $438,183.3; and acarbose $503,116.7. The incremental cost of metformine + sibutramine is $2,589.1 and acarbose is an alternative dominated by metformine. CONCLUSIONS Metformine + sibutramine is a costeffective alternative from the institutional perspective, in order to accomplish the weight loss in patients with diabetes mellitus type 2, with obesity or overweight in Mexico