The results of cross - sectional descriptive study using qualitative and quantitative method about diseases in school, social vices and bad habits of 10th grade students in two high schools in Nam Dinh province showed that: (1) Most students had correct understanding on diseases in school, social vices and bad habits
96.3 percent of students knew that seat for reading and studying should be enough light
92.4 percent of students knew to sit on right posture
93.2 percent of students knew to brush the teeth regularly
91.9 percent of students knew to take a shower with clean water to protect the skin
92.6 percent of students knew that the learning neglect was the harmful effect of game addiction
91.5 percent of students knew that the disadvantage of game was effective to the eyes
97.1 percent of students knew that smoking led to the risks of lung disease
95.3 percent of students knew that drinking alcohol was harmful to the health. (2) However, a considerable proportion of students awared incompletely, especially students in rural area
15.9 percent of students did not know any preventive measure to protect the eyes
11.1 percent of students could not list any disease in school. Two recommendations were proposed that: (1) Social, school and family should focus on educating the knowledge on diseases in school, bad habits and social vices prevention. (2) The education sector should concern more about training and communicating the above knowledge for students in rural areas, especially in remote areas.