The paper deals with simulations of steady-state continuous chemical processes. Currently, user-friendly universal simulation programs are available, which free the user from routine programming work and allow him/her to concentrate effort on creative work. Despite their seemingly easy use, maximum caution is to be maintained when dealing with industrial problems. Some problems associated with realization of simulation calculations including instruction for their solutions are described. The aim of this paper is to contribute to enhanced reliability of simulation calculations and to increase economic efficiency of simulations.