This study focused on cognitive representations of low back pain patients receiving chiropractic (n = 213) versus physiotherapy treatment (n = 125). Variables assessed included satisfaction with care, illness perceptions, beliefs about pain and medicines, attitudes towards doctors and medicine, suffering, adherence and functional incapacity. In the chiropractic treatment, functional incapacity was predicted by painful symptoms, suffering and personal control, and in the physiotherapy treatment by age, pain intensity, positive suffering, care satisfaction, illness identity and medication adherence. The groups differed on all cognitive variables assessed. Interventions should take into consideration cognitive dimensions, across treatment modalities.