The most recent official census by the Comoran government, conducted in 1991, put the islands' population, exclusive of Mahoré, at 446,817. Official counts put the population of Mahoré at 67,167 in 1985 and 94,410 in 1991--a 40 % increase in just six years. Average population density in Comoros was 183 persons per square kilometer in 1980. This figure concealed a great disparity between the republic's most crowded island, Nzwani, which had a density of 470 persons per square kilometer in 1991; Njazidja, which had a density of 250 persons per square kilometer in 1991; and Mwali, where the 1991 population density figure was 120 persons per square kilometer. Overall population density increased to about 285 persons per square kilometer by 1994. Mahoré's population density went from 179 persons per square kilometer in 1985 to 251 per square kilometer in 1991.

The islanders reflect a variety of origins. Malay immigrants and Arab traders have mixed with peoples from Madagascar and with various African peoples. Most of the islands' inhabitants speak island-specific varieties of Comorian, a Bantu language related to Swahili. Comorian, Arabic, and French are the official languages, with French being the language of administration. Islam is the state religion. Ngazidja has about half of the nation's population, while Mwali has just 5 %; Moroni is the main population centre. The birth and death rates are both high in the Comoros, and, although infant mortality is a major problem, the population growth rate is about twice the world average. Almost half of the population is less than 15 years of age.