Unusual FDG uptake in unilateral breast on FDG PET study in a 32-year-old lactating woman with recent diagnosis of left upper lobe hydatid cyst is described. The FDG PET study demonstrated uptake in the periphery of the lesion corresponding to the hydatid cyst. In addition, there was an unusually intense FDG tracer uptake in the right breast. She was questioned about her breastfeeding practice in view of the unilateral uptake, and she gave a history of feeding her child from the right breast only. This case gives insight into the fact that there is differential glucose transporter activity in lactating women related to breastfeeding practice as evidenced by unilateral FDG uptake in breast.