Molar incisor hypomineralization (MIH) is defined as an idiopathic qualitative enamel defect affecting first permanent molars and incisors, caused by changes in the initial stage of mineralization or during ameloblast maturation. Numerous researches have been conducted on the prevalence of this defect which has been reported in a wide range. This paper aims to analyze the occurrence of molar incisor hypomineralization in literature throughout the world and to compare the results according to different diagnostic criteria. Papers found by searching PubMed® database have been compared according to diagnostic criteria, region, age and number of participants and the prevalence of MIH. The papers without a defined diagnostic criteria, as well as papers not written in English, were excluded from the comparison. Out of 62 valid papers in English published in the period from 2000 to 2018, only 35 of them included EAPD (The European Academy of Paediatric Dentistry) 2003 diagnostic criteria. The age of participants ranged from 5.5 to 17 years, with the highest concentration being from age 7 to 9 years, while the prevalence of MIH ranged from 2.8% to 44%. The analysis of the conducted researches is difficult to carry out since different diagnostic criteria, methods and participants age groups were used. Future papers should focus on harmonizing criteria and methods in order to obtain significant data through their comparison.