The paper presents the division of Holocene into four palynostratigraphical units: early, Holocene, middle Holocene, late Holocene - older part, and late Holocene - younger part. It stresses that the best defined border is that between the Late Glacial and early Holocene, and all other "borders" have the character of broad transitional zones. The attention is also paid to the complex of changes starting between 4000 and 3000 BP connected with the retreat of hazel and oak and expansion of hornbeam and beech with fir spreading in the south and spruce in the north-east of Poland. From ca. 6000 BP on the human activities cause increasing changes in vegetation that are difficult to be distinguished from those generated by natural factor.