To determine the association between military expenditure (ME) and public investment efficiency, I regressed a measure of public investment effectiveness upon a measure of ME in a cross-section of 59 developing countries. A strong association was only observed for Sub-Saharan Africa. One of the main explanations for the strong association is a relatively big government which was accompanied by government operations being inefficient and corrupt. This served as a reason to separately observe group of regions with relatively small and big governments. The results confirmed that the effect of ME on public investment effectiveness in the group with a relatively big government is negative whereas the effect is positive in group of region with small governments. Thus, it confirms that the increase of ME is not always negative but can in some cases improve the effectiveness of public investment.