Fair share of ethnic Russians in the areas occupied by Finland during WW II were placed into internment (or concentration) camps - nominally 'transfer camp'. Like other closed systems in Finland in 1941-42 people in the camps faced significantly higher mortality rate than the rest of the population. Though it was not intentional. Of the imprisoned ethnic Russians (at highest ~24 000 were in the camps, or around 30% of the ethnic Russians remaining in the occupied area) around 4 500 perished - primarily due to malnutrition.

This was result of several different factors. Perhaps most importantly early on it was believed that the war (Continuation War) would be a short one and end rather quickly so no real preparations for long term internment or imprisonment were made. Second was that that Finland was following the start of the WW II (loss of fertilizer imports) and the Winter War (loss of arable land) unable to produce enough food for the people even if the army had not been mobilized. Since it was the situation was bordering catastrophic (famine) which affected the worst the people interned or imprisoned to the camps. Third factor which existed was that Finnish occupational control favored early on certain ethnicities over the others (mainly those considered to be kin to Finns, i.e. Karelians, Ingrians, Izhorians etc.).

On the other hand people do not seem to have been confined to camps just because of their ethnicity - not solely at least. Karelia captured by the Finns had been ravaged by the war (scorched earth policies were to some extent used by the withdrawing Soviets) and there simply was no place for a fair number of people to live. Another factor was that Finns did not want to allow civilians to live near the front lines - and the places where the front lines stopped (river Svir, Petrozavodsk, Medvezhyegorsk) were areas with significant number of ethnic Russian residents in Karelia. Also the expectations of a short war followed with repatriations of civilians led to assumptions that ethnic Russians from the captured areas could be 'exchanged' with people of Finnic (Karelian, Ingrian, etc.) heritage. Lastly Finnish occupational control (military) did want to minimize problems with Soviet partisans and it was typical that people from the areas with notable partisan activity would be made to relocate. Often to the camps.

The camps themselves are a different story. Some were Soviet prison camps - others just city blocks (of Petrozavodsk) without any fences around them - at the start that is. So the conditions between the camps varied significantly. Additionally several diseases spread very easily in the confined population and Finns had to start to take measures to both confine and disinfect the population. On the other hand when it became obvious that the war would not be a short one Finns worked to move people out from the camps back to their homes or for example to farms in safe areas (as in safe from partisans).