Indexes used in orthodontics are an important instrument for diagnosing occlusion and teeth abnormalities. They help to minimize the influence of an examining person’s subjective evaluation and, to a certain extent, enable standardization of the relationships within a dental arch as well as between dental arches. They are also indispensable tools in epidemiological studies of occlusion defects and make it possible to assess the scale of the problem in a studied population, as well as facilitate planning of prophylactic and therapeutic activities.The paper presents the currently used orthodontic indexes. Some of them enable identification of a given abnormality (diagnostic indexes), while others allow for assessment of the frequency of a given abnormality, its intensity, and as a consequence, therapeutic needs (occlusion indexes). There are also indexes that have only historical significance (Pont’s index). The paper addresses in detail the application and the method of using the most frequently used diagnostic indexes, as well as occlusion indexes, being more complex instruments in the hands of an orthodontist.