In recent years there has been a growing interest to investigate how emotions affect logical reasoning. There is evidence that emotional states and emotional task contents could impede performance on logical reasoning problems. The aim of our research was to investigate how strong emotions occurring due to spider phobia affect logical reasoning. Therefore, spider phobics and non-phobics completed a conditional inference task with different types of content: spider phobia relevant, negative, and neutral problems were presented. The results showed that spider phobics performed worst on phobia relevant problems compared to neutral and negative inferences. Thus, processing anxiety relevant topics may elicit a fear response resulting in a decrease of cognitive resources which might be responsible for the impaired reasoning performance.