Our aim was to compare the need for analgesics/drugs of abuse between headache patients--chronic and episodic headache sufferers--and addicts, by the Leeds Dependence Questionnaire (LDQ). This is a self-completion 10-item instrument to measure dependence upon a variety of substances. We administered the LDQ questionnaire to 122 chronic daily headache (CDH) sufferers who had been taking one dose of analgesic drug every day for at least 1 year; 71 subjects suffering from episodic headache (EH) using analgesics only occasionally; 115 consecutive drug addicts (DA) with a diagnosis of substance dependence. The mean LDQ total score was similar in the CDH (11.58+/-6.35) and DA (10.37+/-6.51) groups, and for both it was significantly higher than the score in the EH (5.61+/-3.00) group (P<0.001). The CDH group had the highest scores, and higher scores than the DA group (Z=-8.18, P<0.001) in item 8, assessing the primacy of effect over the kind of analgesic used, and in item 10 (Z=-5.03, P<0.001), asking if it is difficult to live without the analgesic; the DA group had the highest scores, and higher scores than the CDH group, in item 9 (Z=-5.07, P<0.001) addressing the need for the continued administration of the drug to maintain well-being, and in item 3 (Z=-2.39, P<0.05), exploring compulsion to start the use of the drug. The EH group had lower scores in all items (P<0.05) except for item 9, where there was no difference from CDH group; the EH group had also lower scores (P<0.001) than the DA group, except for item 8, where, instead, the score was higher than in the DA group (Z=-5.33, P<0.001). A strong link develops between chronic headache patients and the analgesics they use. This sort of 'dependence' appears to be a consequence of headache, originating from the necessity for the analgesic to cope with everyday life.