Data were extracted from the Cancer Registry of Norway that administers BreastScreen Norway. The screening program started in 1996 and offers biennial mammography to women aged 50-69 years (7). Information about 4309 women screened and diagnosed with breast cancer, 3333 with screen-detected cancer and 976 with interval cancer, during the period January 1, 2007 – December 31, 2020, was included in the study. Breast volume (cm3) and fibroglandular volume (cm3) were measured by a fully-automated software for breast density assessment (Volpara, versions 1.5.0 and 1.5.4.0) (8, 9). Mean breast and fibroglandular volume were plotted by age at diagnosis for women with screen-detected and interval cancer with locally weighted scatterplot smoothing. Logistic regression was used to identify the odds ratio (OR) with 95% confidence interval (CI) of interval cancer for quartiles of breast volume (1: 48.2 – 558.5 cm3; 2: 559.0-820.8 cm3; 3: 821.0-1166.7 cm3; 4: 1167.1-3031.8 cm3), including screen-detected cancer as reference and adjusting for fibroglandular volume (cm3) and age at diagnosis (years).