It is quite common for logging while drilling (LWD) tools to be unstable and the acquired data to be of poor quality. This is why quality control of LWD data is of utmost importance. Common methods of quality control for wireline logs in vertical wells often do not show good results in horizontal wells because of vertical and horizontal heterogeneity of reservoir rocks. A quality control system and the ways to control the quality of common LWD methods are discussed in the thesis. Two approaches to control the quality of LWD methods are considered in the thesis. One of them is cross-plot analysis and comparison of obtained logs with offset wells and core data. The other is solution of direct and inverse problem from obtained well logs. The methods are compared to a typical way of histogram analysis and normalization. Examples of poor and good quality logs are analyzed in detail. In addition, problems, which could be encountered if proper quality control is not used, are discussed. The result of the thesis is a quality control system for processed LWD data in horizontal wells. The approach was tested in various lithological conditions: siliciclastic, salinated and carbonate reservoirs. The proposed system could be used to avoid poor decision-making during the process of geosteering and well completion.