Objective To assess the incidence of lichen sclerosus (LS) in women and the all‐cause and cause‐specific mortality of women with LS. Design Population‐based descriptive study. Setting Finland. Population All Finnish women, including 7790 women diagnosed with LS during the period 1969–2012. Methods Information gathered from the Finnish Hospital Discharge Register on women with LS was combined with dates and causes of death from Statistics Finland and the Finnish Cancer Registry. Population statistics are from Statistics Finland. Main outcome measures Crude and age‐adjusted incidence rates of LS and standardised mortality ratios (SMRs). Results The incidence rate of LS adjusted for age (European Standard Population) increased from 14 per 100 000 woman‐years in 2003 to 22 per 100 000 woman‐years in 2010–2012. The age‐specific incidence rate was highest in postmenopausal women (24–53 per 100 000) but was also elevated in girls aged 5–9 years (seven per 100 000). The all‐cause mortality of women with LS was lower than in the general female population (SMR 0.84, 95% CI 0.78–0.90), mostly as a result of decreased mortality from circulatory diseases (SMR 0.80, 95% CI 0.72–0.89) and dementia and Alzheimer’s disease (SMR 0.75, 95% CI 0.62–0.88). The cancer mortality equalled that of the population, but the vulvar cancer mortality was increased (SMR 28.1, 95% CI 19.3–39.4). Conclusions Lichen sclerosus is a common disease of elderly women. The overall mortality is decreased whereas the mortality as a result of vulvar cancer is increased. Tweetable The likelihood of getting LS by age 80 years is 1.6%. The mortality of women with LS is reduced compared with that of the population. Tweetable The likelihood of getting LS by 80 years is 1.6%. The mortality of women with LS is reduced compared with that of the population.