The article describes a genesis of Social Building Societies in Poland starting from the National Housing Fund through Workers Housing Estates Society in 1934-1939, New Housing Order of 1993 announcing a development of the cheap building, up to Barbara Blida's and Irena Herbst's legislative initiative of 1995 leading to establish the Social Building Societies. According to International Permanent Social Building Committee social housing means supply of houses with fixed minimum standard of comfort and equipment, for rent or sale for persons who can not afford a house at market price without assistance of state or social organizations. In Poland, the Social Building Societies cannot supply houses for sale but only for rent. State assistance in supplying houses for rent consists in establishing purposeful fund and providing it with financial means to allow credits on preferential conditions. National Housing Fund allows the Social Building Societies large, cheap and long term credits, bearing interest at a half rediscount rate in NBP but not lower then 4,5%. The Social Building Societies solve housing shortage problem by transformation of existing housing needs in demand, anticipating average households future incomes to pay off credit during almost 30 years. Social Building Societies are like a hybrid, because they have to fulfil social mission as well as maximize financial profit from their activity. Construction of Social Building Societies lead to creation of a closed market on which Social Building Societies play on demand side on the building market as well as on supply side on the housing market.The authoress describes Social Building Societies' activity from tne legal side as well as on the financial side including status, organization forms, territorial location, financial source for their activity, rent policy, housing assets management, SWOT analysis and criteria of the Social Building Societies investment projects evaluation.