Objectives: Breast and colon cancer are neoplasms well known to be related to obesity. Adiponectin, a proteinthat increases in obesity, seems to be involved in the relationship but clinical data are limited. Methods: In thisstudy, we therefore evaluated the serum adiponectin levels in 87 breast and 27 colon cancer patients and assessedthe relation with BMI, menopausal status, receptor status and stage of disease. Results: Serum adiponectin levelswere lower in cancer cases (8583 ± 2095 ng/ml for breast cancer, 9513 ± 2276 for colon cancer) than in controls(13905 ± 3263). Conclusion: A low serum adiponectin level may be associated with both breast and colon cancer,and that this association is not statistically significant for either receptor or menopausal status in breast cancergroups.