The work aims to identify the most promising lines of own maize breeding on productivity and resistance to various environmental factors. It involves them in breeding work to create hybrids maize with an earliness index FAO 200-300. Maize is one of the major crops on the planet. This crop is associated with a high grain yield and, of course, with the versatility of use. One of the main conditions in increasing the production of a grain of corn hybrids is the study and identification of promising lines with high combination ability and the production of high-yielding mixtures on their basis. These hybrids are improved options for the breeding process, possessing economically valuable traits that are resistant to biotic and abiotic environmental factors. This work on getting and studying maize hybrids resistant to various factors (bio- and abiotic) is highly relevant for breeders of research institutions currently conducting research in maize breeding. The subject of research, investigations on the study of the selfed line of maize of own selection on economically valuable characteristics, as well as on resistance to biotic factors of the environment, were carried out. The authors laid out the experiments and evaluated the lines based on the institute in the foothill zone of Kabardino-Balkaria in 2020–2021. The authors carried out the experiments according to the methods of field experiments. According to the results obtained in the research, the following lines were distinguished: 92C0112, 92C5183, 92C543, 92C005, 92C0112, 92C5183, 92C267, 92C543, 92C06146, 92C5183, 92C267, 92C06146, 92C0206, 92C0241, which are of breeding value. According to yield data (from a working plot), the following numbers can be distinguished: 92C0247, 92C267, 92C281, and 92C0206. In the conditions of the foothill zone, the authors studied the lines of productivity and resistance of corn cobs to the primary diseases and pests found in the fields of the republic. This study was the scientific novelty of the research. Selected lines will be used in breeding work to obtain high-yield maize hybrids.