OBJECTIVES: To examine factors associated with total time and cost of providing care for patients with dementia in outpatient clinics at a university hospital in Bangkok. METHODS: Primary caregivers for patients with dementia diagnosed with probable Alzheimer’s disease or vascular dementia and receiving medical care from outpatient clinics were selected.  Data were collected from primary caregivers using questionnaires during February 1 - July 31, 2007. Dependent variable was total time or total cost of providing care by family members without financial compensation (informal care) or other caregivers with financial compensation (formal care). Independent variables were demographic factors of primary caregivers (e.g., age, gender, education, and occupation), relationship with patients, and disease severity of patients. Univariate and multivariate statistical analyses were applied.  RESULTS: Informal care cost accounted for 82% of total cost of providing care. Patients with moderate to severe (parameter estimate, PE = 0.897, p<0.002) or severe dementia (PE = 1.785; p<0.001) needed significantly longer time of care compared to those with mild dementia. Patient’s spouse provided less time of taking care compared to hired caregivers or patient’s child (PE =-1.159, p<0.001). In addition, patients with severe dementia significantly consumed higher cost of providing care compared to those with mild or moderate to severe dementia (PE=1.611, p<0.001). Primary caregivers with bachelor degree or higher (PE=1.054, p<0.007) or receiving financial compensation (PE=0.901, p<0.045) significantly increased the total cost of providing care. The models investigating the factors associated with total time or cost of providing care could explain approximately 41% or 31%, respectively. CONCLUSIONS: Informal care cost can lead to a significant economic burden to the families of patients with dementia in Thailand.  Factors associated with total time and cost of providing care may help develop the healthcare system of providing care for patients with dementia in the future.