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One of the classifications of atmospheric circulation types applied in Poland is the typology proposed by Lityński (1969). Circulation types were designated based on three classes in each of three indices (zonal Ws, meridional Wp, and cyclonicity index Cp). Indices Ws and Wp were developed based on differences in atmospheric pressure over the area of 40°-65°N and 0°-35vE. A total of 27 types were designated. Calendars of the types in reference to the period 1951-1999 were published. Lack of information on particular stages of development of the calendars seems to preclude unequivocal interpretation in their use. It is not clear what reference period was considered in the development of the calendars. An example is provided that a change in the reference period causes the shift of 5% of days to another class. The name of the type does not always concern the direction of air advection. For example, in January, the middle class „0" zonal index is characterised by air advection from the west. In such a situation, the type called „S" in practice describes inflow of air from direction „SW". An example is also provided of a situation where the same value of the Wp index was qualified in June to class „S", and in November to class „N". Examples of analyses are also presented with the application of daily values of Wp and Ws concerning air temperature, snow cover, and UTCI index. Attention is drawn to the need of high degree of caution in the interpretation of research concerning multi-annual periods where results of reanalyses were used as source data. It is pointed out that the annual courses of circulation indices Wp and Ws may be approximated when the determination of air density considered the same temperature in reference to all days in a year. [ABSTRACT FROM AUTHOR]