The T-34/76, known simply as T-34 in Russia, is a designation for all T-34 models with a 76mm cannon. The 76mm versions were produced during the first years of World War 2 and only a limited amount was used after the war. Since 1943 the 76mm models were replaced by the 85mm models.
T-34/76 Model 1940: The Model 1940 was the first production model and had a 76mm L-11 cannon.
T-34/76 Model 1941: The Model 1941 was fitted with the superior 76mm F-34 cannon.
T-34/76 Model 1942: The Model 1942 has a hexagonal turret and is the most common variant.
T-34/57: The T-34/57 is fitted with the high velocity 57mm ZiS-4 cannon that has a better performance against tanks but reduced performance against other targets.
OT-34: Some Model 1941 and Model 1942 tanks were fitted with a flamethrower instead of a bow machine gun and were known as OT-34.

The T-34/85, known as T-34-85 in Russia, features a more powerful 85mm cannon in a larger turret. The 85mm models are by far the most common post war models.
T-34/85 Model 1943: The Model 1943 was the first in the T-34/85 lineup and features the D-5T cannon.
T-34/85 Model 1944: The Model 1944 has a simpler ZiS-S-53 gun and features serveral other changes that include an improved internal layout and new gunner's sight.
T-34/85 Model 1945: The Model 1945 features an electric traverse motor and a smoke system.
T-34/85 Model 1946: The latest model to be produced in the USSR was the Model 1946 that featured and improved engine and new roadwheels.

A limited amount of T-34's have been used as a support vehicle.
T-34-T: The T-34-T was the earliest support vehicle based on the T-34 design. Damaged T-34's were converted to an artillery tractor by removing the turret and having the turret ring plated over.
SPK-5: The SPK-5 was introduced in 1955 and is a T-34 with the turret removed and a 10 t crane mounted on the turret ring.

The Type 58 is a license produced version of the T-34/85 produced in China.
Type 58: The Type 58 is the Chinese production version of the T-34/85 and is fitted with sights used on the Type 59.
Type 58-I: The Type 58-I has a redesigned commander's hatch and has a heavy machine gun on the turret roof.
Type 58-II: The Type 58-II features a second cupola with heavy machine gun mount.

The T-100 is an Egyptian conversion of the T-34 tank that mounts the ordnance of the 100mm BS-3 fieldgun. The turret has been increased in size by welded metal plates and a recoil buffer is installed under the main armament. The 100mm BS-3 has a much better performance against armored vehicles compared to the original armament. It is believed only a small amount of T-34's have been converted to the T-100.

The T-122 is an Egyptian modification of the T-34 that mounts the ordnance of the D-30 howitzer in a much modified T-34 turret. The size of the turret has been significantly inmproved by welded metal plates. Unlike the T-100 conversion the D-30 ordnance has been mounted at the rear of the original T-34 turret. Compared to the T-100 the T-122 has a reduced performance against vehicles but does better against infantry. It is believed that only a small number, perhaps a dozen, have been built.

The T-34/122 is a Syrian modification that combines the T-34 chassis with a the D-30 towed howitzer. The T-34 has its turret removed and a D-30 howitzer without its trails is mounted at the front of the vehicle facing rearwards. A folding platform is attached which is locked in place horizontally when in the firing position. The D-30 howitzer has the same performance as when used on the ground, but has the added benefit of a much improved cross country mobility.