This study aims to demonstrate the degree of effectiveness, of public teaching hospitals, in the use and allocation of production factors, in comparison with public general and private hospitals. Data Envelopment Analysis (D.E.A) was employed with included inputs being (a) the number of beds, (b) the number of employed physicians, (c) the number of employed nursing staff, (d) the number of administrative employees, (e) the total cost for goods and services and (f) the total cost per hospitalized patient, whereas as an output the total number of hospitalized patients was used. This study evaluates the degree of rational use of inputs for a total of 25 Greek (public and private) hospitals for the period 2009-2012 showing a comparative analysis in terms of technical efficiency and scale efficiency. The results show a significant improvement in overall technical efficiency and scale efficiency for the teaching and general public hospitals over private ones. It appears that the significant adjustment imposed in the quantity of production factors (inputs) of the public hospitals, has considerably improved the efficiency levels in contrast to private hospitals for which the change of the mixture and the reallocation of production factors considered to be of great importance.