The purpose of our study was to assess the differences in the water and lipid fractions and lipid line widths in normal breasts between premenopausal and postmenopausal women using single-voxel proton MR spectroscopy (1H-MRS). Thirty-two premenopausal and 25 postmenopausal women were enrolled in the study. Single-voxel proton MR spectroscopy of the breast was performed using point-resolved spectroscopy (PRESS) with water suppression and stimulated echo acquisition mode (STEAM). On STEAM, water fraction 1 was the ratio of the integration of water to the sum of the integration of water and methylene resonances, and the lipid fraction 1 was the ratio of the integration of methylene to water and methylene resonances. Lipid fraction 2 was the ratio of the integration of allylic methylene to water and allylic methylene resonances. Lipid line width was measured on PRESS. The premenopausal group had a higher water fraction 1 and lower lipid fraction 1 than the postmenopausal group (p < 0.01, Student's t test). The breast density had a positive effect on water fraction 1 and a negative effect on lipid fraction 1 for premenopausal women (p = 0.018, multivariate regression) and for the total population (p = 0.019). The premenopausal women had a higher lipid fraction 2 than postmenopausal women without significance (Student's t test), but the premenopausal status had a positive effect on lipid fraction 2 (p = 0.024, multivariate regression). There was no significant correlation between all independent variables and lipid line width. Breast 1H-MRS shows the differences of water and lipid compositions between pre- and postmenopausal women. Lipids containing methylene and allylic methylene protons had different implications in normal breasts.