This paper will review the ways in which the effectiveness of counterterrorism measures and policies has been assessed and argue that they suffer largely from the same difficulties. For many of the chosen indicators it is not clear whether they represent what they are supposed to represent and whether shifts in the scores can be attributed to counterterrorism. After having discussed these problems, a different way of measuring counterterrorism effectiveness is outlined. It rests on the assumption that counterterrorism should be broken down into separate components that should all be evaluated separately. For all components, a causal chain from cause (measure) to effect (shift in indicator) should be formulated to solve the meaning and attribution problems.