The Vietnam Health Insurance Law in 2008 promulgated universal health care by 2014. To build up a sound and sustainable health insurance system towards this goal, we need to account for the effect of asymmetric information on the use of the health care services, namely moral hazards and adverse selection. This paper uses distinc- tive features of Vietnam's health insurance system to separately estimate the effect of each type. Our results show that the effect of asymmetric information is quite severe and prevalent for old people, and is insignificant for young people. The results can be used for the construction of health insurance policies for Vietnam.