Abstract: Models with selective convexity are an important class of data envelopment analysis (DEA) models. This type of model allows managers to consider variables such as ratios, averages, percentages, etc. The paper proposes algorithms for constructing input and output isoquants using volume variables in models with selective convexity. These algorithms help investigate the relationship between any volume variables in the model. Computational experiments confirm the reliability and efficiency of the proposed methods. © Pleiades Publishing, Ltd. 2024. ISSN 0005-1179, Automation and Remote Control, 2024, Vol. 85, No. 1, pp. 79–89. Pleiades Publishing, Ltd., 2024. Russian Text The Author(s), 2024, published in Avtomatika i Telemekhanika, 2024, No. 1, pp. 110–123.