The project studied the robustness of research results on productivity effects of ICT. Particular emphasis was put on the decomposition of growth into the effects of investment and productivity growth and on the heterogeneity of inputs. The project consisted of a macroeconomic and a microeconomic part.The macroeconomic part investigated the robustness of approaches in empirical research on growth that are based on production functions. It compared how different methods, as the estimation of production functions and growth accounting, valuate the contributions of inputs and technical progress to growth. As little analysis had been conducted on this subject so far, it was initially carried out with two factors of production, capital and labour.  The microeconomic part worked with data from the ZEW ICT survey and considered the estimation of the effects of heterogenous ICT components on productivity and innovation. First an overview of methods was worked out. Subsequently a new examplary analysis for the use of business software by firms was carried out. The aspect of heterogeneity played a particular role, because data were available not only for business software but for its different types.