The aim of the study was to examine the effect of livestock production on the economic efficiency of investments in irrigation projects. The study was based on a model focused on field crop/livestock production using the data of crop yields in field crop production with or without irrigation, financial results of cattle fattening and milk production and the input and output price relationship. The influence of livestock production on the economic effects of irrigation system utilization was evaluated using the indices of economic efficiency of investments - internal rate of return, net present value and pay-back period. The data on the amount of investments required for the construction of the irrigation system, economic benefit achieved by optimizing production under both irrigated and non-irrigated conditions, with and without livestock production were used to determine these indices.