The article presents the results of a research into the pressure generated by samples of selected bituminous coals and blends made from these coals during carbonization carried out under the conditions of constant volume and limited expansion. The structure of the apparatus used in research enables the simulation of the effects occurring in the coking chamber affecting the level of pressure generated in the plastic layer in two characteristic coking stages. In the early phase of coking, when plastic layers head for the middle part of the chamber and there is unplasticized coal charge between them (carbonization under the conditions of limited expansion) and at the moment of plastic layers combining in the chamber’s axis (carbonization in constant volume). During research it was found that considerable fluidity of the plastic coal mass forming the charge blend and similar temperature range of plasticity facilitate the generation of high pressure in the plastic layer during coking. Simultaneously, under these conditions high intensity may characterize the migration of the plasticized coal substance outside the area of the plastic layer as well as the compression of the unplasticized part of the charge, that is the effects which relatively lower the pressure in the plastic layer. Adding to the composition of the blend coal generating higher pressure during carbonization than other components and plasticizing within the same temperature range as other ingredients of the blend, we have to take into account the rise of the pressure generated by such a charge. Whereas effective reduction of the coking pressure may be attained by adding to the charge coal plasticizing in significantly lower temperatures than other coals even if it is characterized by high coking pressure.