Sleep-related attentional bias has been proposed to be an important factor in the development and maintenance of primary insomnia. In this study, a newly introduced mixed modality (visual auditory) task and an emotional Stroop task were used to investigate attentional processes in patients with primary insomnia, sleep experts and healthy controls (n = 20 per group). The sleep expert group served as second control group to control for effects of frequency of concept usage (FOCU). The results of the emotional Stroop task showed a sleep-related attentional bias in the insomnia group in comparison with the expert group. However, no significant differences were detected in the other group comparisons and in the mixed modality task. The difference between insomnia patients and sleep experts in the emotional Stroop task indicates that FOCU is not the underlying process of sleep-related attentional bias. Insomnia patients seem to be more emotionally, cognitively or procedurally affected by sleep-related stimuli than sleep experts. The findings suggest that a desensitization of sleep-related stimuli might be used therapeutically, thus extending the current cognitive behavioral treatments for primary insomnia.