83 Articles Kalina Kavaldzhieva * Summary: A major problem in investments in the healthcare and social systems is the efficiency of the investment, the optimization of the social infrastructure, whether people (consumers) will be able to afford the services offered by the new assets - subject of the investment. To answer these questions the following should be considered: ways of forming cash flows to calculate the cost of services, pricing of services, analyzing the purchasing power of the population, affordability and financial sustainability. Keywords: social cost, social price, cash flow, NPV, IRR, affordability and financial sustainability JEL Classification: H430 Project Evaluation; Social Discount Rate 1. Introduction T o improve the quality of life, measures for the optimization and modernization of the social infrastructure are taken, which will contribute to the human capital of the labour market in conformity with the goals of the Lisbon convention. Communications from the Commission to Efficiency оf the Capital Invested in Oncological Care Measured by Social Affordability * Assistant professor at the Department of Accounting and Analysis, UNWE, e-mail: kalinakavaldzhieva@gmail.com. the Council, the European Parliament, the European Economic and Social Committee and the Committee of the Regions, Action Against Cancer: European Partnership, Brussels, 24.6.2009 and resolution at the 58th World Health Assembly resolution on prevention and control of cancer, WHO 2005. All these documents ensure social sustainable development in terms of social and health infrastructure. Basic prerequisite for deciding whether to make such investments is how effectively the capital will be invested in healthcare, whether this capital will be socially tolerated by all households or they will rely on different donor programs. The main purpose of this article is: to examine the possibilities of capital investment made to modernize and reconstruct the medical institutions, to investigate how effective the invested capital will be. In the study the principles of economic assessment are observed. Resources invested in a project are valued at their opportunity cost and output - on consumers‘ willingness to pay for them. It should be pointed out that the opportunity cost does not necessarily correspond to the observed financial cost; similarly, willingness to pay is not in all cases accurately revealed by observed market prices, which may