The LaGG-3 rapidly replaced the LaGG-1, although the new fighter was too heavy for its engine. In fact, Lavochkin, Gorbunov and Gudkov had originally designed their prototype for the powerful Klimov M-106 engine. But it proved to be unreliable. So they were obliged to install the relatively weak Klimov M-105P. As a result, the LaGG was slow; its top speed was just 575 km/h, while its rate of climb, at ground level, was as slow as 8.5 meters/second. The LaGG-3 proved to be somewhat hard to control as it reacted sluggishly to stick forces. In particular, it was difficult to pull out of a dive, and if the stick was pulled too hard, it tended to fall into a spin. As a consequence, sharp turns were difficult to perform. A more powerful version of the engine was installed, but the improvement was small, so the only solution was to lighten the airframe. The LaGG team re-examined the design and pared down the structure as much as possible. Fixed slats were added to the wings to improve climb and maneuverability and further weight was saved by installing lighter armament (most versions used a 1 × 20 mm ShVAK cannon and a single synchronized 12.7 mm Berezin UBS machine gun). But the improvement was slight and, thus, without an alternative powerplant, when the LaGG-3 was first committed to combat in July 1941, it was completely outclassed by the Messerschmitt Bf 109.
Later in 1941, the LaGG-3 appeared with new armament options, an internally balanced rudder, retractable ski landing gear for the winter, retractable tailwheel and wing pipes for drop tanks. The result was still not good enough. Even with the lighter airframe and revised supercharged engine, the LaGG-3 was underpowered.
The LaGG-3 proved immensely unpopular with pilots. Some aircraft supplied to the front line were up to 40 km/h (25 mph) slower than they should have been and some were not airworthy. This happened less because of the added weight with full gas and weapon loads in combat conditions, but specifically to the poor finishing in rushed industrial production, due to the German invasion. In combat, the LaGG-3's main advantage was its strong airframe. Although the laminated wood did not burn, it shattered when hit by high explosive rounds.
The LaGG-3 was improved during production, resulting in 66 minor variants in the 6,528 that were built. Experiments with fitting a Shvetsov M-82 radial engine to the LaGG-3 airframe finally solved the power problem, and led to the Lavochkin La-5 The major LaGG-3 construction plant in Gorky switched over to the La-5 in 1942, after having completed 3,583 LaGG-3. All further LaGG-3 development and production was done by factory 31 in Taganrog as the sole LaGG-3 manufacturer.
Soviet pilots generally disliked this aircraft. Pilot Viktor M. Sinaisky recalled: "It was an unpleasant client! Preparing the LaGG-3 for flight demanded more time in comparison with other planes. All cylinders were supposed to be synchronized: God forbid you from shifting the gas distribution! We were strictly forbidden to touch the engine! But there were constant problems with water-cooled engines in winter: specially as there was no anti-freeze liquid. You couldn't keep the engine running all night long, so you had to pour hot water into the cooling system, in the morning. Furthermore, pilots didn't like flying the LaGG-3 - a heavy beast with a weak M-105 engine - but they got used to it. Even so, we had higher losses on LaGG-3 than on I-16s."
Contrary to popular belief, the nickname lakirovannie garantirovanny grob ("(the) varnished guaranteed coffin" - varnished guaranteed coffin) was not used during the war.
Even with its limitations, some Soviet pilots managed to reach the status of ace flying the LaGG-3. G.I. Grigor'yev, from 178.IAP, was credited of at least 11 air victories plus two shared. But pictures of his LaGG-3 "Yellow 6", in November–December 1941, show 15 "stars", so his score was probably higher.