Departing from traditional project management, this article focuses on cultural and localized differences and influences on a specific project activity, and furthermore on the specific influences on large important critical projects (also called megaprojects). It analyzes relevant methodologies, theories and results from other disciplines such as micro-behaviors influenced by local cultures, socio-cultural theories, cultural synergy processes and hybrid institutions, physioeconomics as well as different practices in contracting. It is shown that the very definitions of the concept of are diverse in the world, and details are given. A scaled gap analysis tool is proposed, rooted in the above theories and results, aiming at identifying cultural differences between megaprojects from a set of qualitative measures. To further allow for causal analysis, a set of cultural impact measures is proposed, and the same sample of international megaprojects is assessed correspondingly. The tool has allowed analyzing a sample of 16 documented international megaprojects on 5 continents. The taxonomy of the cultural attributes and causal impacts allows grouping the megaprojects by clusters of similar culturally driven management styles, irrespective of implementation countries. Taking thereafter the viewpoint of characterizing a given regional culture, it is shown that Scandinavian project management practices evidence a specific combination of cultural influence measures relying on hybrid governance and communications, unique work culture and tools, as well as an approach to adaptation. The paper finally discusses ethical characteristics of megaprojects, to conjecture that the alternatives are far fewer and more globalized. The conclusion shows that, despite the fact that to apprehend cultural factors in general is a very complex endeavor; the limited set of cultural influence measures identified here allows characterizing cultural impact on megaprojects. Megaprojects can be clustered or contrasted by cultural influences, by mana. This article focuses on cultural differences and influences on a specific project activity, and furthermore on the specific influences on the execution outcomes of large important critical projects (also called megaprojects). It analyzes relevant methodologies, theories and results from other disciplines such as cross-cultural analysis, micro-behaviors influenced by local cultures, sociocultural theories, cultural synergy processes and hybrid institutions, physioeconomics as well as different practices in contracting. It is shown that the very definitions of the concept of are diverse in the world, and details are given. A set of 16 megaproject cultural attributes, and of impact attributes, is proposed. A scaled gap analysis is enabled, rooted in the above theories and results, aiming at identifying cultural differences between megaprojects and project outcomes, from the proposed attributes. That analysis is applied to a sample of 16 documented international megaprojects on 5 continents. The taxonomy of the cultural attributes and causal impacts allows grouping the megaprojects by clusters of similar culturally driven management styles, irrespective of implementation countries and national cultures. Megaprojects can now be clustered or contrasted by cultural influences, by management styles, thus serving concrete needs in megaproject management Taking thereafter the viewpoint of characterizing a given regional culture, it is shown that Scandinavian project management practices evidence a specific combination of cultural influence measures relying on hybrid governance and communications, unique work culture and tools, as well as an approach to adaptation. The paper finally discusses ethical characteristics of megaprojects, to conjecture that the alternatives are few and more globalized.