This study was planned to investigate leptin levels under different models of nutrition and their relation with anthropometric parameters in early infancy. Sixty four infants (28 exclusively breast-fed, 15 exclusively formula-fed and 21 mixed-fed), aged 4 months were included and their leptin, insulin-like growth factor-I (IGF-I), and IGF binding protein-3 (IGFBP-3) levels were measured. Leptin, IGF-I and IGFBP-3 levels of the three groups were not statistically different (P > 0.05). The results of our study questions the role of leptin as a link between nutritional pattern and adiposity-growth in early infancy.