Purpose: The purpose of this article was to analyze the perceived impact of Industry 4.0 technology on the functioning of companies in the context of implementing the Lean philosophy. Although the literature emphasizes the complementarity of both approaches, there is still a lack of empirical data showing how these assumptions are realized in practice. This study fills this gap by showing to what extent technologies such as IoT, BDA, CPS, DT, MES and robotics are evaluated as catalysts for Lean transformation. Methodology: the survey was quantitative in nature and was conducted in the form of a questionnaire to representatives of manufacturing companies. The impact of the six technologies on eight areas of the company’s operations (e.g. efficiency, costs, environment, working conditions) was evaluated. Friedman’s test, Kendall’s coefficient and principal component analysis (PCA) were used in the analysis. Results: The highest rated technologies were robotics, IoT and MES. Respondents differentiated the impact of individual technologies, but the level of agreement between their ratings was low. Principal component analysis showed that some technologies are perceived to be interrelated and form coherent groups of impact, especially in terms of efficiency and cost. The differences in evaluations indicate that the integration of Lean and Industry 4.0 takes place in a heterogeneous way and depends on the organizational context. Value: The article contributes to the research on Lean 4.0 by showing the discrepancies between declarations and actual practice and identifying key challenges for effective digital transformation with Lean in mind.