Abstract: The interpretation of ‘lean production’ has been slowly shifting from technical to socio-technical aspects since its appearance. This is well illustrated by the growing number of expressions associated with lean like ‘lean management’ and ‘lean thinking’. Seeking more advanced and at the same time more successful ways of lean implementation, researchers and practitioners discovered that carefully adding human, behavioural, management, leadership and many other soft elements in the lean melting-pot, will most likely improve application results. Still, despite all the efforts made, the socio-technical definition of lean is still blurry, researcher-dependent and mostly not confirmed by evidence. This study introduces a unified, cultural definition of lean integrating the culture model of Schein and the lean model from Modig and Åhlström. It shows that lean could be interpreted in different abstraction levels, as basic underlying assumptions, espoused values, methods and tools, giving an interrelated definition for each. The study also presents the findings of an empirical quantitative questionnaire research verifying the ‘lean culture’ definition and identifying correlations between ‘lean culture’, corporate competitiveness and corporate characteristics, based on information from 193 participating Hungarian medium and large sized industrial companies. The data show that the underlying assumptions of lean culture named Objective waste elimination, System level rationalization and Vision is improvement are significantly correlated with the components of corporate competitiveness. The findings draw attention to the soft, cultural side of lean production implementation and give practical advice on methods how to shape and control the cultural aspects of the implementation process to improve the chances of success.