We investigated the practical applicability of the PTAS for solving problems of P2|prec, p ∈ 1, 2|Cmax class using the solution of the corresponding problem of P2|prec, p = 1|Cmax class. Problems from the second class are solved by four polynomial algorithms: Coffman’s, Sethi’s, Gabow’s and Fujii’s ones. The dependences of the absolute and relative error of the obtained solution using the proposed method on the dimensionality of the problem and the density of the corresponding precedence graph were studied. In particular, statistics for in-trees, out-trees and sets of chains were calculated. The results of numerical experiments we carried out show that the solution of the original NP-hard problem using the proposed method is optimal in more than 80.