In a prospective randomised study with a 2-year follow-up, 103 patients were randomised to anterior cervical decompression and fusion (ACDF) with a cervical carbon-fibre intervertebral fusion cage (CIFC) or the Cloward procedure (CP). The purpose of the present study was to report predictors for fusion and also to investigate the importance of radiological variables for the clinical outcome. Gender, age, smoking habits, disc height, segmental kyphosis and type of surgical procedure were used as independent (before surgery) variables in a multiple regression model. Male gender, one-level surgery and CP treatment were significant predictors of fusion and explained 14% of the variability of fusion status at follow-up. Number of levels operated on, however, did not influence the clinical outcome. Fifty-two per cent of the women and 17% of the men in the CIFC group, and 25% of the women and 8% of the men in the CP group, had pseudarthrosis. Although patients with a healed fusion had significantly less pain intensity than patients with pseudarthrosis, radiological variables explained only 4% of the variability of pain at follow-up. Apart from a significant correlation between preoperative kyphosis and neck disability index at follow-up, no significant correlation between either postoperative kyphosis or preoperative or postoperative disc height and clinical outcome was found. Neither degree of segmental kyphosis nor disc height was different between patients with healed fusion and pseudarthrosis. One can conclude that male gender and type of surgery were significant predictors for a healed fusion and that pseudarthrosis affected outcome. In contrast to the commonly held view based mainly on theoretical considerations, no effect on clinical outcome could be demonstrated for segmental kyphosis and disc height at follow-up. Overall, the study shows that the importance of radiological factors as predictors for fusion as well as clinical outcome is limited.