The article describes history of reformation in the region of north-ern Mazovia which belonged to the Roman catholic diocese of Płock. In comparison to other districts of Polish Republic the region was national-ly homogenous, with substantial number of minor gentry and strong economic bonds between the gentry and Roman Catholic Church. The above mentioned factors together with skillful and effective activities of bishops of Płock and Jesuit Society (which concentrated mainly on catholic reformation) were the main reasons for episodic character of reformation churches in the region of Mazovia. A few reformation churches that existed for a short period in the region where the place of origin for many famous representatives of reformation. Nevertheless due to unfavorable situation in their native region they had to move somewhere else.