• portfolio complexity
• patent portfolio
• multiplicity
• interrelatedness
• forward citations
• firm's size
• firm's performance
• backward citations
• portfolio diversity
• research and development

This thesis is the result of the internship carried out from September 2014 to March 2015 at the Cardiff Business School, in Wales. During this period, I studied the relationship between patent portfolios and firm's economical performance. The management of patent portfolio is indeed an onerous activity and it is necessary to understand which are the variables to leverage on in order to obtain better results. Patent portfolio complexity is the result of the interaction of three main characteristics: diversity, multiplicity and interrelatedness. Various combination of these elements and the effect of other contextual variables influence firm's profitability. To my research, I collected data of 391 international manufacturing firms and I studied the relationship between patent portfolio diversity and firm's performance. In a later stage, I analyzed the moderating effect on this relationship of multiplicity and interrelatedness and other four variables: forward and backward citations, firm's size and R&D expenditures. Results show an inverted-U shaped relationship between patent portfolio diversity and performance affected by the moderating effect of variables considered. Therefore results contribute to explain the relationship between patent portfolio complexity and firm's performance and raise new interesting questions for future research.