Purpose. Taking the customer-centric nature of integrated marketing communications (IMC), this article investigates the specific role of customer performance in IMC effectiveness in various size companies applying inter-country context. Design/methodology/approach. The sample consists of the primary data from developed (Spain) and developing (Belarus) economies. A total of 540 manager respondents participated in the survey. The article uses structural equation modeling and multi-group analysis for analysis. Findings. When taking into consideration, customer performance affects the IMC outcome on the market and financial performance. The customer performance role varies in firms of various sizes and small- and medium -sized enterprises (SMEs) operating both in developed and developing economies. Research limitations/implications. The research underlines the significant role of customer pe...