The differences in growth patterns in breast-fed (BF) and formula-fed (FF) infants remain poorly understood. The aim of this study was to examine the relation of serum ghrelin and leptin concentrations to the different growth patterns between the formula-fed and breast-fed babies. Feeding behaviors and anthropometric data were noted at the 3rd and 6th months of age. Serum ghrelin and leptin levels in both groups and breast-milk ghrelin and leptin levels in the mothers of the BF group were determined at the 3rd month of age. Body weight, length, TSF (triceps skin fold thickness), postnatal weight gain, and serum ghrelin levels were higher in BF babies than in the FF group. In BF babies, serum ghrelin was correlated to TSF, and serum leptin was correlated to weight, TSF and weight gain at three months of age. As the serum leptin increased, energy intake from supplemental foods decreased in the BF group at the 6th month. Higher serum ghrelin in BF babies might have played a role in their faster growth rate during the first three months of age. On the other hand, lower energy intake from supplemental foods in correlation with higher serum leptin in BF babies may explain why these babies show marked decline in growth rate compared to FF babies after three months of age.