The Polish Border Guard (SG) detained in excess of 4,300 illegal immigrants in 2014, over 800 more than in 2013.
According to statistics compiled by the SG's headquarters, Ukrainians were most frequently apprehended (2,000 people), a rise of 100 percent on the previous year.
There was also an 80 percent rise in the number of Vietnamese detained without the correct documents (420 people).
Other nationalities prominent on the list were Russians (264), Belarusians, Georgians and Syrians.
While Vietnamese and Syrians often regard Poland as a gateway to the West, Ukrainians typically want to stay in Poland to find work.
With Kiev currently at war with pro-Russian separatists in eastern Ukraine, the SG found that most of the detained citizens had forged visas or employment documents.