PURPOSE: Cancer treatment is increasingly delivered in an outpatient setting. This may entail a considerable economic burden for family members and friends who support patients/survivors. We estimated financial and time costs associated with informal care for colorectal cancer. METHODS: Two hundred twenty-eight carers of colorectal cancer survivors diagnosed on October 2007-September 2009 were sent a questionnaire. Informal care costs included hospital- and domestic-based foregone caregiver time, travel expenses and out-of-pocket (OOP) costs during two phases: diagnosis and treatment and ongoing care (previous 30 days). Multiple regression was used to determine cost predictors. RESULTS: One hundred fifty-four completed questionnaires were received (response rate¿=¿68 \%). In the diagnosis and treatment phase, weekly informal care costs per person were: hospital-based costs, incurred by 99 \% of carers, mean¿=¿\textlesseuro\textgreater393 (interquartile range (IQR), \textlesseuro\textgreater131-\textlesseuro\textgreater541); domestic-based time costs, incurred by 85 \%, mean¿=¿\textlesseuro\textgreater609 (IQR