ABSTRACT Background - The fourth most frequent tumor in the world, colorectal cancer is commonly diagnosed at an advanced stage. Objective - To analyze factors that interfere in the diagnosis of colorectal cancer in users of the Public Health System treated at an universitary hospital in Curitiba, Paraná State, Brazil. Methods - Cross-sectional, quantitative and descriptive study with 120 patients treated at the institution between 2012 and 2013. Data collection, carried out by means of medical record appointments and patients' interviews, addressed sociodemographic variables; clinical profile; timespan between symptoms, examination, diagnosis, treatment onset and difficulties encountered. Statistical analyses were performed by means of Stata 8.0. Results - Abdominal pain was the most frequent complaint and rectal bleeding presented the highest chance of advanced colorectal cancer diagnosis. From 52.5% of patients with late diagnosis of colorectal cancer, 81% reported difficulties in the health system. Conclusion - Results suggest that late diagnosis is due to symptom absence in the early stage of the disease, patients' lack of perception about the severity of the symptoms, need of better of health teams to search early diagnosis. Educational interventions are deemed necessary to the population and health teams, besides actions prioritizing the access to diagnostic testing for serious illnesses.