Background: Ethological methods used to analyze human obsessive-compulsive disorder (OCD) rituals demonstrated excess of unnecessary repetitions as well as irrelevant, idiosyncratic acts (additions) compared to normal activity. A question that still remains is whether these well-known repetitions and additions are manifested in behaviors unrelated to the OCD rituals. Our objectives were to: (1) assess whether OCD-related repetitions and additions as found in previous studies also affect the patients' activity of filling out questionnaires and (2) evaluate the specificity of these behaviors to OCD as opposed to other anxiety disorders and healthy controls. Sampling and Methods: Several standardized disorder-specific self-report questionnaires were used in order to assess the patient's psychopathologies. The style of filling-out these questionnaires by OCD and non-OCD anxiety outpatients and normal controls was analyzed. Four categories were used: omissions, repetitions, corrections, and additions. Results: The OCD group scored significantly higher on the number of additions as compared with both the anxiety group and the nonclinical group, and significantly higher on the number of corrections and repetitions as compared with the nonclinical group. Conclusions: The hallmarks of OCD, repetitions and additions, are manifested not only in the patient's rituals and thoughts, but in apparently “neutral” tasks that do not a priori involve the intrusive thoughts, urges, and images typical of obsessive-compulsive behavior. Additions seem to be more specific to OCD than repetitions. These two executive faults impede routine functionality of OCD patients in tasks related and unrelated to their rituals. Our study delineates simple, observable behavioral characteristics that distinguish between OCD and non-OCD anxiety patients as well as healthy individuals. These symptomatic behaviors may offer a clue to personality traits or deficits in executive functions that possibly play a part in the pathophysiology of OCD. Our results are an additional indication that nonfunctionality in obsessive-compulsive behavior deserves full attention for a better understanding of the psychopathological mechanisms of OCD.