The demographic composition of the area the 19th and early 20th centuries is unclear as many factors contributed to the ethnic orientation of the people; out of these religion was particularly important thus giving rise to a proselytism struggle between the Greek
Ecumenical Patriarchate of Constantinople and the
Bulgarian Exarchate (established in 1870). In 1886, 78.4% of the Christian population of the Florina
kaza (district) - a part of
Manastir Vilayet (province) - was aligned with the Ecumenical Patriarchate and 21.6% with the Bulgarian Exarchate, however by 1900 the Patriarchatists had dropped to 50.9% and Exarchatists had risen to 49.1%. In 1914 the majority of the Christian population of the Florina district was recorded as Exarchist Bulgarian (59%), 70% of whom were monolingual in Bulgarian only. The 1920s was a period of migration, displacement, deportation and a voluntary exchange of populations between Greece and Bulgaria, during which the Greek government aimed to remove Slavic-speakers with fanatic Bulgarian sentiments from Greek Macedonia.). In 1925, according to the Prefect of Florina 52% of the population were schismatics (up from about 20% in 1886), 25% were Patriarchists, 15% were
refugees, 6% were Vlachs (
Aromanians) and 3% were indigenous Greeks. According to government sources, in 1925 there were 45,527 Slav speakers, of whom 34,234 former Exarchists and 11,293 former Patriarchists; 7449 Greek refugees; 3590 Vlachs (Aromanians); 1882 indigenous Greeks; 349 Jews and 27 Muslim Albanians. According to Kollopoulos in 1925 the recorded Slav Macedonians were 64,465 and constituted 64% of the population of the district of Florina, of whom 28,673 were schismatic. The 1928 census showed 38,562 Slavic speakers in the nome of Florina or 31% of the population, but according to contemporary Greek authors the numbers of this census "clearly" do not reflect the actual strength of the minority as a result of official policy and Greek government of reluctance. According to the Prefect of Florina, P. Kalligas, in 1930 there were 76,370 (61%), of whom 61,950 (49% of the population) lacked Greek consciousness, while his successor V. Balkos estimates those speaking Bulgarian as 75-80% of the population of the nome in 1931. The local
Greek population includes a linguistic minority of bilingual
Slavophones, who in the early 1990s formed about 64% of the rural population and about 16% of the prefecture's total population."
Anastasia Karakasidou estimated that 80% of the population of Florina Prefecture is either Slavic-speaking or descended from Slavic-speaking families. There also exist smaller communities of
Aromanians and
Arvanites, which today mostly have an ethnic Greek identity. A diverse range of
dialects are spoken in the regional unit alongside the official
standard and local
Macedonian varieties of
Greek. A minority of people speak the local
ethnic Macedonian dialects and especially the
Lower Prespa dialect and the
Prilep-Bitola dialect. According to the 2021 census, the population of Florina regional unit was 44,880 people. ==Agriculture==