The paper presents the results of studies on carbonate cements of Hauterivian-Oligocene sandstones from the Silesian Unit (Polish Flysch Carpathians). Petrographic observations included 70 samples of thick-bedded, fluxoturbiditic (Fx) and turbiditic (Ta) sandstones which showed highest carbonate contents among all the Silesian Unit flysch members (Tab. 11). In these samples principal fabric components (Q, F, R, M), cement and CaC03 were measured (Tab. 1, 3, 4, 8). Moreover, variability of crystal size of carbonate cements was determined quantitatively (Tab. 2, 5, 6, 9) along with their genesis. The results demonstrate regularity in distribution and crystal size of genetically different cements in calcareous sandstones of the Silesian Unit. The regularity is dependent on the age and burial depth ot sandstones. The Oligocene thick-bedded Krosno Sandstones reveal the presence of very finecrystalline calcite cement (Tab. 2). As the only studied sandstones they also contain predominantly dolomitic matrix (Tab. 1) and dolostone clasts of diversified textures. The clasts were redeposited from the marginal zone of the basin where sedimentary environment favoured carbonate deposition (including dolomite). The calcite cement of the Krosno Sandstones precipitated relatively very rapidly from supersaturated pore solutions at the presence of abundant crystallization nuclei originating from the incompletely dissolved calcitic matrix. The increasing content of carbonate cement is accompanied by its decreasing crystal size (Fig. 4). Calcite cement of the Eocene-Turonian thick-bedded, calcareous sandstones known from the Ciężkowice, Istebna and Godula Beds (Tab. 11) originates exclusively from diagenetic cementation process. On the contrary to the Krosno Sandstones, this cement is medium- to coarse-crystalline (Tab. 5, 6) and does not contain carbonate matrix. The finest-crystalline calcite fractions originate from cementation processes, as well. This cement was precipitated from supersaturated pore solutions. Precipitation of calcite took place relatively early, at relatively shallow burial depths. Cementation resulted in hardening of the fabric. In co-existing sandstones devoid of or poor in carbonate mineraIs the prolonged compaction led to densification of fabric and appearance of concave-convex grain contacts. The increasing calcite cementation is accompanied by increasing crystal size in the Ciężkowice and Istebna Sandstones (Fig. 2, Tab. 4) or decreasing crystal size in the Godula Sandstone (Fig. 3). Correlation coefficients between the cement content and the crystal size of calcite reach maximum positive and negative values for the average crystal diameters (Mz) or for the crystal diameters most typical of the given sandstone unit (Tab. 7). The Grodziszcze Sandstones located in the lowest part of Hauterivian-Barremian succession contain recrystallized calcite cement which shows highest percentage and largest crystal size among all the studied sandstones. Very coarse- and coarse-crystalline (Tab. 8, 9) cement of the Grodziszcze Sandstones originated from recrystallization of not only primary matrix but also finest fraction of limestone lithoclasts. This recrystallization was related to the significant burial depth accompanied by high pressure and increased temperature. The Lgota Sandstones (Albian-Cenomanian) contain only single layers of calcareous sandstones (up to 1.2 meters thick). Their calcite cement originated from cementation or recrystallization of detrital carbonate grains. Calcite produced by recrystallization is more abundant and shows larger diameters than calcite derived from cementation processes (Tab. 8, 9). Moreover, microcrystalline silica which always accompany calcite cement is absent.