This paper attempts to at least partially redress a paucity of current literature on the joint analysis of inter and intra firm diffusion of innovations within as well as across countries. In particular, by using two data sets derived from independent country-specific surveys, it undertakes an international comparison of inter and intra firm diffusion of Information and Communication Technology (ICT) use in the UK and Switzerland. This allows one to address many of the problems that have prevented general conclusions on the drivers of inter and intra firm ICT adoption decisions. An encompassing model is proposed which gives quite satisfactory results for both countries. It is found that inter and intra firm ICT adoption decisions are driven by different factors, confirming the findings of Battisti and Stoneman [Battisti, G. and Stoneman, P. (2003) Inter and Intra Firm Effects in the Diffusion of New process Technology. Research Policy, 32, 1641–1655; Battisti, G. and Stoneman, P. (2005) The Intra Firm Diffusion of New Process Technologies. International Journal of Industrial organisation 23, 1–22.] and Hollenstein and Woerter [Hollenstein, H. and Woerter, M. (2004) The Decision to Adopt Internet-based E-commerce. An Empirical Analysis Based on Swiss Firm-level Data. KOF Working paper NG 89, Zurich.] that ‘first use’ and ‘intensification of use’ represent independent choices. The study also suggests that significant differences exist between the UK and Switzerland, probably as a result of their differing diffusion stages. In addition the importance of new organisational and managerial practices as drivers of diffusion stressed by recent theoretical and empirical work is supported for both countries. Overall the findings suggest that comparative research is a promising way to identify robust relationships and should be explored further.