Objective: To compare the mammogarphic appearance between breast cancer patients aged <40 and ${geq}40$ years. Methods: Needle localization and biopsy of suspicious mammographic lesions identified 1,959 breast carcinomas in a single institution from Jun 2012 to Apr 2013. According to the age, we divided patients into two groups: <40 and ${geq}40$ years old, and analyzed mammographic appearance separately. Results: Young patients had 44.2% foci with calcification, but old patients only had 39.4% (P<0.001). In younger group, the ratios of cases according to mass density were 41.8% or higher, 58.2% equivalent and lower. In older group, the ratios were 55.5 % and 44.5%, respectively. There were statistical differences between high density and others (P<0.05). The ratios of cases according to mass margin were 13.9% circumscribed and microlobulated, 86.1% indistinct and spiculated in the younger group, as compared to 6.5% and 93.5%, respectively, in the older group (P<0.05). Conclusions: Mammographic findings differ between young and old patients with breast cancer, for example regarding mass density, mass margin and microcalcification ratios.