The development of a decision support system for assessing the suitability of the water for irrigation aims to protect cultivated crops not to be irrigated with water of unsuitable quality. Discussed are the estimation algorithm, based on the methodology, and the general description of the computer programme, following them. The algorithm includes three fundamental steps: establishing of an irrigation water quality indicators database, assessment of the irrigation water quality and issuing recommendations for irrigation water utilization. The programme structure of the system, which is the topic of this paper, contains three modules: input data uploading and updating; assessment of the irrigation water quality; preparation of recommendations. The results are presented in groups: Potential irrigation problems, specific toxicity, miscellaneous effects, choice of recommendation related to the obtained indicators.