Background In Japan, the prevalence of constipation-predominant irritable bowel syndrome (IBS-C) and functional constipation (FC) diagnosed by the Rome III criteria is unclear, as are the demographic profile, quality of life (QOL), and habits of persons with IBS-C or FC. Methods We performed an internet survey of constipation. After extracting 3000 persons fitting the composition of the general Japanese population, we investigated demographic factors, lifestyle, defecation, and laxatives. IBS-C and FC were diagnosed by Rome III criteria. Respondents also completed the Japanese IBS severity index (IBS-SI-J), Japanese IBS QOL scale (IBS-QOL-J), SF-8, Hospital Anxiety and Depression Scale (HADS), and Japanese Health Practice Index (JHPI). Results There were 262 respondents with FC (8.73%) [73 men and 189 women; mean age: 49.8 ± 13.1 years; mean body mass index (BMI): 21.0 ± 3.3 g/m2] and 149 respondents with IBS-C (4.97%) (76 men and 73 women; mean age; 41.6 ± 13.7 years; mean BMI: 20.8 ± 3.0 kg/m2). Total IBS-QOL-J score were significantly lower in the IBS-C group than the FC group. With regard to SF-8, score of mental component summary (MCS) was significantly lower in the IBS-C group. The total IBS-SI-J score and item scores, except for satisfactory defecation, were significantly higher in the IBS-C group than the FC group. HADS showed a significant increase of anxiety and depression in both the groups, and the JHPI revealed insufficient sleep. Conclusions In Japan, among the population of under 70 years old, the prevalence of IBS-C and FC (Rome III criteria) was 4.97% and 8.76%, respectively. IBS-C caused more severe symptoms than FC, resulting in impairment of QOL. Electronic supplementary material The online version of this article (10.1007/s00535-019-01611-8) contains supplementary material, which is available to authorized users.