The association between breast volume and breast cancer risk has been shown to vary by age and ethnicity (1). Breast volume measurements were, however, based on subjective or two-dimensional assessments, while the amount of fibroglandular tissue was not considered (1, 2). In recent years, fully-automated systems for mammographic density assessment have been able to generate objective measurements of breast density and volume, providing the opportunity for studying the associations with breast cancer risk with higher precision than in previous studies (3). Mammographically dense breasts have been shown to be more common in women with interval cancer compared to those with screen-detected cancer (4). The evidence on a possible association between breast volume and breast cancer by detection mode is limited (5, 6). We aimed to explore the odds of interval versus screen-detected breast cancer by breast volume in participants of an organized breast cancer screening program, BreastScreen Norway.