A court in Ha Giang province in the northern mountains also sentenced five other members of the gang to life in jail after 50 people were tried for trafficking heroin and weapons and bribery.
The ring smuggled around 840kgs of heroin and 70 handguns to provinces bordering China to sell to Chinese customers.
Truong Phat Hoa, Pham Van Duong, and Pham Van Tuan were the three drug lords getting capital punishment.
Nguyen Ba Ly, a former senior drug enforcement official in Ha Giang, got a life sentence along with Nguyen Tien Nuoi, Hoang Van Mao, Pham Xuan Loc, Sung Quang Phan, and Pham Thi Duc of the gang.
Ly was also indicted for offering bribes worth US$10,000 to investigators to bale out the drug gang.
Other members received jail terms ranging from three to 20 years.
The ring was busted in late 2004 after police arrested Tran Huu Thuy and Lai Trung Thong for illegally transporting weapons.
The two snitched on the ring to investigators.
The police said Thuy and Thong would be tried separately.
Vietnam has some of the toughest drug laws in the world. Anyone found guilty of possessing, trading, or trafficking 600 grams (1.32 lbs) of heroin or 20 kilograms (44 lbs) of opium will face the firing squad.