Non-disclosure of deferrable risk has received little attention in the literature. We examined deferrable risk (history of intravenous drug use [IVDU]) and donor attitudes towards truthfulness, the screening process and interpretation of the screening question as well as risk profile. Donors negative for all markers with a self-reported history of IVDU (N = 30) and matched controls were identified from an anonymous mail-out survey. In a separate survey, hepatitis C virus (HCV)-positive donors participated in a telephone interview, from which all those with IVDU history (N = 29) were selected plus matched controls (combined total 59 IVDU, 236 controls). IVDU donors, when compared with matched controls, tended to believe that it is OK not to answer truthfully if one believes that her/his blood is safe (18.6% vs. 4.7%) and that some questions are a little too personal (35.6% vs. 21.7%). IVDU donors were more likely than controls to say they failed to acknowledge screening questions appropriately (23% vs. 2.2%) or to agree that IVDU questions are mainly about recent drug taking or sharing needles (29% vs. 11%) even though the screening question asked about IVDU ever without any such qualifiers. IVDU donors were also more likely to have other lifestyle/risk factors such as history of sex with IVDU (45.5% vs. 1.7%). Donors with deferrable IVDU history may rationalise that revealing their status is not necessary and may misinterpret the question. Failure to acknowledge risk behaviour is complex, and some degree of non-disclosure may be an inherent part of pre-donation screening.