While nearly three-quarters of cancer mortalities occur in low- and middle-income countries, we know little about the factors contributing to patient delays in seeking care for cancer. Our study employs a multifactorial approach by examining three key areas: patient socio-demographic factors, structural factors of health-care access and cancer patients' beliefs about their illness and cancer in general as potential determinants of their delay in seeking care in Thailand. We conducted a cross-sectional study using a systematic sample of 264 patients with cancer treated during 2006-2007 at Prince Maha Vajiralongkorn Cancer Centre, a hospital of the National Cancer Institute of Thailand. We defined patient delay as when a patient waited more than 3 months after symptom onset to seek medical care. We used bivariate analysis and multivariate logistic regression to examine unadjusted and adjusted associations of patient delays in seeking care with: patient socio-demographic factors, structural factors of health-care access and patients' beliefs about their illness in particular and about cancer in general. We also obtained patient self-reports about their reasons for delaying care. In multivariate analysis, only patient-belief factors were significantly associated with delay. Patients who believed that the primary causes of cancer were non-medical (vs. medical) were more likely to delay seeking care (adjusted odds ratio (OR)=4.37, 95% confidence interval (CI)=2.27-8.67). Patients who believed that cancer was probably curable or was curable (vs. incurable) were significantly less likely to delay seeking care (adjusted OR=0.2, 95% CI=0.08-0.56; adjusted OR=0.18, 95% CI=0.07-0.49, respectively). Patient socio-demographic factors and structural factors of health-care access were not significantly associated (p>0.05). Our findings suggest that interventions to reduce delays in care seeking should address patient beliefs regarding cancer in order to effectively mitigate barriers to access.