Edited and copied from Ecotopia Wiki "Routes in the Baltic States"
Poland Cycling on roads or pavement is not allowed when there is a bike path/lane. You can get fined for it, as well as for jay walking. At traffic lights, even if there are no cars coming, you still have to wait for green.
Belarus Since there are almost no private properties it is very easy to wild-camp in Belarus. In cities you may not cycle on roads. You have to use sidewalks instead, otherwise you might get fined by the police. But it is not so strict in small towns. Countryside roads are generally of a good quality. It is not recommended to cycle on M class roads (especially M2-M6 and M9) because of heavy traffic. The roads through fields without proper coverage should be avoided.
Lithuania Avoid whenever possible is called in Lithuanian "zvyras" or "zvyro danga" (translated to "gravel", but you should not mistake it with the nice gravel found for example in Scandinavia). This is a horrible mixture of sand and small hard bumps, unsuitable for cycling.
Often it is better to take "gruntinis kelias" (unimproved road) if asfalt is not available.
Low population density - not so many shops, drinking water sources etc.