The effects of board size and board composition on various measures of firm performance is a well researched topic in the area of corporate governance research; the main focus of this research has been on the US market but in the last years more research in other developed and developing economies has emerged as well. Research on board size does currently not exist for the German market, but board composition has been examined mainly regarding two unique characteristics of German supervisory boards: first, codetermination, i.e., the mandated employee representation, and second, the representation of bank employees on the board. Based on the most comprehensive data set in German corporate governance research thus far, I consider the effects of board size and board composition on 1) market valuation and performance, 2) earnings management, and 3) cash holdings. The unique data set includes all major German listed companies from a ten year period (1998-2007, n=294, with some 2,400 observations). The results of my analyses vary: while no consistent effect of either board size or board composition on firm valuation and performance can be found, the latter does have a signifi-cant impact on earnings management: female directors are associated with less earnings man-agement. Eventually, I find lower levels of cash holdings for firms with smaller boards and with employee representatives on their boards. The mixed results clearly show the limitations of empirical research in this area: these three outcomes suggest that board size and board composition should be considered carefully when structuring a company as well as when investing in certain firms. In contrast, the crea-tion of a "general strategy" with regards to board size and composition is not advisable.