This research aims at establishing whether national culture has an impact on the internal adoption and use of Web 2. 0 in organizations, and providing an explanation to how this may be happening. The rationale for it was derived from two factors. The initial indication that such impact can exist came from the evident skewness in the distribution of levels of activity on Wikipedia shown by representatives of different countries. The analysis of the literature dedicated to Knowledge Management, national culture and Web 2. 0 also highlighted theoretical reasons for culture-dependence in Web 2. 0's adoption and use. Achieving the aim in a robust manner required fulfilling a number of objectives. First, it had to be proven that there was a correlation between the national culture and the propensity to use Web 2. 0 sites. Second, it was necessary to verify whether the same trends held in an organizational context, and (third) an explanation had to be sought as to what the underlying mechanisms could be. The evidence gathered via a combination of quantitative and qualitative methods shows that indeed, there is evidence that the national culture does play a role in the degree and the way Web 2. 0 is used in organizations, and provides an explanation of the mechanisms involved. The thesis makes a fundamental contribution by expanding the existing body of literature into an unexplored area lying at the intersection of national culture, Web 2. 0 and Knowledge Management, and by highlighting and addressing the limitations in the theories used.