The analysis and the assessment of maintenance costs for technological equipment play a dominant role among maintenance management issues in industrial enterprises. An original approach to this problem is based on the non-maintenance costs which can be defined through the expenses caused by the non-maintenance of the functional characteristics of industrial technological equipment. Practically, the equipment inefficiency (non-maintenance) costs can be assessed by the difference between provisioned operation cost to be obtained in an ideal situation (according to which the equipment dose not undergo any breakdown) and the real situation of the results obtained in the same period. The assessment model for non- maintenance costs proposed in the paper involves the covering of the following stages: diagnosis, the definition of ideal situation, the evaluation of the results' accounts and the calculation of the non-maintenance cost as such.