This book is devoted to the analysis of functioning of the G20 at the leaders' level as a relatively new international cooperation club existing since 2008 where top-level representatives of systemically significant countries meet, authorised to make decisions which are of key importance for the international community. The book is divided in two parts. The first part shows the origin, course and meaning of specific historical/political processes which led to the emergence of G20 Leaders'. Also, cause and effect relationships have been indicated and conclusions drawn with regard to the significance and further functioning of the group. Part two is the analysis of preparation, course and effects of subsequent G20 summits in the years 2008-2013.