The present study investigated the relationships between pain-related fear, attention to pain, and pain intensity in daily life in patients with chronic low back pain. An experience sampling methodology was used in which electronic diary data were collected by means of palmtop computers from 40 chronic low back pain patients who were followed for one week. Attention to pain was hypothesized to mediate the relation between pain-related fear and pain intensity. Further, pain-related fear as a trait characteristic was expected to moderate the relation between attention to pain and pain intensity. Multi-level analysis was used for all analyses. Although the tested mediation models yielded statistically significant mediation effects, the sizes of these effects were relatively small and clinically irrelevant. Instead, results suggested that pain-related fear and attention to pain independently predicted pain intensity. No evidence for moderation of the relation between attention to pain and pain intensity by pain-related fear as a trait characteristic was found. Implications of the results from this study are discussed and suggestions for future research are provided.