The objective of this study is, based on the existing literature, to provide a general systematic characteristic of market structure models. We distinguish cost, production, profit, revenue functions, as well as the general identification approach as most plausible methods to measure the degree of market power. Using time-series data of the Ukrainian milk processing industry, as an example, we utilized the production approach to estimate the exercise of oligopsony power, test functional forms and verify estimation methods. The results of two-equation models did not produce any evidence suggesting the exercise of market power, whereas, the three-equation models revealed the presence of oligopsony.