During the two decades of 21st century, growth of the knowledge on the distribution of Cucujus cinnaberinus in Poland was substantial. Numerous new records were published, mainly from Eastern part of the country. In contrast, distribution of a flat bark beetle in western Poland is less studied, and the species is significantly more rare in this part of Poland. In the present paper records from five regions of western Poland are reported in detail: (1) area of Słubice and Frankfurt (Oder) (“Łęgi koło Słubic” and German “Odertal Frankfurt-Lebus mit Pontischen Hängen“ nature reserves), (2) Trzebnica Ridge – the central part of Trzebnica Hills, (3) Widawa and Odra valleys near Wrocław, (4) Garb Chełmu area, and (5) “Rozumice” nature reserve. In the case of Słubice and Wrocław areas, C. cinnaberinus inhabits floodplain forests with domination of oak stands but significant number of records in the vicinity of Wrocław were noted in poplar plantations. In Trzebnica Hills, C. cinnaberinus inhabits oaks, sycamores and aspens in scattered patches of broadleaved forests. In the area of Chełm and in “Rozumice” nature reserve, C. cinnaberinus occurs in oak-hornbeam forests.Old maps of all the above mentioned areas were studied to gather data on the history of forests during the last 200 years (in some cases it was possible to trace the forest history to the 2nd half of 18th century). In most cases, C. cinnaberinus occurs in forests that show ecological continuity during this period of time. The only exception is the vicinity of Słubice, where forests were either absent or only young, presumably floodplain forests, were present in the areas where C. cinnaberinus occurs nowadays. It is concluded, that although C. cinnaberinus can inhabit secondary forests and poplar plantations, it still shows strong affinity to ancient forests. Although many studies showed that C. cinnaberinus can inhabit secondary forests and other anthropogenic habitats, our observations suggest, that at least at a local scale, it can be an indicator of ancient forests. It is recommended to collect further data on the distribution of this species and to conduct studies focusing on phylogeography and genetics of this species to address this problem.