The aim of this study is to characterize the financial structure of the large and medium companies located at Aburra Valley, belonging to the medical and dental services cluster. It wants to determine whether the behavior of this structure coincides with the position of Pecking Older Theory (Myer, 1984) and also, if it has variations during the economic recession period. The results suggest that the large company's financing decisions can be explained from the studied theory, with doesn't find a support in the case of medium companies that changes its financing structure during the economic crisis period, in which intensifies the use of short-term liabilities.