Background Breast cancer is the most frequent malignancy among women worldwide and the second most common cause of cancer-related death in developed countries. The aim of the present analysis is to describe trends in incidence, mortality, prevalence, and relative survival in Denmark from 1980 to 2012 focusing on age, comparing persons aged 70 years or more with those aged less than 70 years. Material and methods Cancer of the breast was defined as ICD-10 code C50. Data derived from the NORDCAN database with comparable data on cancer incidence, mortality, prevalence and relative survival in the Nordic countries, where the Danish data were delivered from the Danish Cancer Registry and the Danish Cause of Death Registry with follow-up for death or emigration until the end of 2013. Results The proportion of patients diagnosed with breast cancer over the age of 70 years increased with time to 29% of women and 44% of men in 2012. Incidence rates increased with time and peaked around 2010 in all age groups except for those aged 90 years or more. Mortality rates were clearly separated by age with increasing mortality rates by increasing age group for both women and men. Relative survival increased over time in all age groups, but patients aged 70 years or more had a poorer relative survival than those aged less than 70 years. In 2012, 58 521 persons (all ages) were alive in Denmark after a diagnosis of breast cancer. Conclusion Poorer survival of Danish breast cancer patients over the age of 70 years is likely to be due to inferior treatment and non-adherence to treatment guidelines. There is a need for clinical trials focusing on patients over the age of 70 years.