Introduction Portfolio Risk Assessment Models are the models that are used to determine the factors affecting the profitability of the stocks included in the portfolio and to assess the risks associated with these factors. There are a large number of models that assess portfolio risk, but there is no unanimous opinion among scientists about what model is better and which model is worse. In this paper, the models of portfolio risk assessment will be considered, as well as their advantages and disadvantages. Capital Asset Pricing Model, Three-Factor Fama-French Model and Five-Factor Fama-French Model will be tested on 100 random portfolios. To simplify data collection and simplify calculations, portfolios will be collected from companies included in the index S&P500. The purpose of the work is to identify which model is the best way to assess risks. The overall aim of this research is to evaluate the effectiveness of different multi-factor models and find the one which has a greater explanatory power. The hypothesis of the study is as follows: one of the CAPM, FF3 and FF5 models project risk of the portfolio better that. The objectives are: 1. To describe portfolio risk assessment models. 2. To find significant factors affecting the stock price 3. To compare models for a set of portfolios In this paper, the model will be evaluated using fundamental and market data over the period 2017 to 2021. A significant limitation of this study is that its results highly depend on the portfolios, used for the research and the chosen period. This study contributed to the financial field by identifying the model that best describes portfolio risk.