Information and Communication Technologies (ICT) developments, in many different strands, are growing continuously with high rates, and are seen as an engine of growth for the world economy. The objective of this article is to analyse the non-linear impacts of ICT on economic growth in large panel data covering 126 countries over the period 2002-2017, by employing data on ICT diffusion, particularly internet, mobile and fixed phone subscriptions, and two indexes purpose-built. The results suggest that ICT diffusion has a positive effect on economic growth, but the marginal positive effect lessen as ICT diffusion enlarges and Internet penetration has greater effects than the mobile phone. The quality of governance is also a crucial determinant of economic growth. Some countries need to develop strategies to promote and increase the effects of ICT diffusion on economic growth.