Overoptimistic predictions are common in software engineering projects, e.g., the average software project cost overrun is about 30%. This paper examines the use of two popular general tests of optimism (the ASQ and the LOT-R test) to select software engineers that are less likely to provide overoptimistic predictions. A necessary, but not sufficient, condition for this use is that there is a strong relationship between optimism score, as measured by the ASQ and LOT-R tests, and predictions. We report from two experiments on this topic. The experiments suggest that the relation between optimism score as measured by ASQ or LOT-R and predictions is too weak to enable a use of these optimism measurement instruments to select more realistic estimators in software organizations. Our results also suggest that a person’s general level of optimism and over-optimistic predictions of performance are, to a large extent, unrelated.