Objective: This study evaluated the role of patients’ associated oral and extra-oral factors, as well as previous dental treatment, as possible predisposing (triggering) factors in the development delusional halitosis. Method: Forty-six patients diagnosed of delusional halitosis, over a consecutive period of 2 years (2003- 2004) were selected for this study. Diagnosis was based on: use of standard halitosis questionnaire (to confirm the presence of psychological component)
modified to obtain data on oral and extra-oral factors, as well as previous dental treatment linked by patients as cause of oral malodour; clinical assessment without objective evidence of oral malodour; absence of reliable third party to confirm patients’ claim of oral
malodour; and screening with sulphur monitor (RH-17 Series Halimeter, Interscan, Chatsworth, CA) that was within normal range (80-140ppb).
Results: All the 46 patients studied had normal halimeter measurement and no reliable third party to confirm the patients’ claim of oral  malodour. Twenty-four (52.2%) patients had associated possible predisposing factors. The most common associated factors were bitter
taste (25.0%), oral deposits (20.8%), carious tooth (16.7%) and previous tooth extraction (16.7%). Associated factors were divided into oral, extra-oral and dental treatment. Patients’ associated oral factors were significantly correlated as predisposing factors for delusional
halitosis (p