Objective: This study aimed to determine differences in sleep quality between patients with mechanical neck pain, patients with whiplash (WAD) pain, and healthy controls and to determine the relationship between the intensity of ongoing pain, disability, and sleep quality. Design: Nineteen patients with mechanical neck pain (4 men, 15 women; age, 40 +/- 16 yrs), 22 with WAD (4 men, 18 women; age, 38 +/- 15 yrs), and 18 comparable controls (4 men, 14 women; age, 41 +/- 13 yrs) completed the Pittsburgh Sleep Quality Index to assess sleep quality. A numerical pain rate scale (0-10) and the Neck Disability Index (0-50) were collected for assessing neck pain and disability. Results: Significant differences in sleep quality (P < 0.001), sleep latency (P = 0.005), sleep efficiency (P = 0.002), sleep disturbances (P G 0.001), use of sleeping medication (P < 0.001), daytime dysfunction (P G 0.001), and total Pittsburgh Sleep Quality Index score (P < 0.001) but not for sleep duration (P = 0.096) were found; patients with mechanical neck pain and WAD pain exhibited higher scores in all components compared with healthy controls. Seventeen (77%) patients with WAD and 13 (68%) with mechanical neck pain reported poor sleep quality (Pittsburgh Sleep Quality Index score, >8). Significant positive correlations between mean intensity of ongoing pain with sleep quality (r(s) = 0.693; P < 0.001); sleep duration (r(s) = 0.433; P = 0.044); sleep efficiency (r(s) = 0.644; P = 0.001) and total Pittsburgh Sleep Quality Index score (r(s) = 0.643; P = 0.001) were found in patients with WAD pain; the higher the intensity of ongoing pain, the worse the sleep quality. Conclusions: Sleep disturbances are a common finding in individuals with neck pain and are associated with the intensity of ongoing pain in WAD. It seems essential to address the ongoing cycle of pain and sleep disturbances as an integral part of the treatment of patients with neck pain.