(Click on the column title to sort by that column)
| # | Catholics | Population | Percent Catholic | Diocese | Year | Source |
|---|---|---|---|---|---|---|
| 1 | 1,660,000 | 1,712,000 | 96.96% | Katowice (Archdiocese) | 2004 | ap2005 |
| 2 | 1,566,555 | 1,618,593 | 96.78% | Kraków {Cracow} (Archdiocese) | 2004 | ap2005 |
| 3 | 1,537,630 | 1,598,630 | 96.18% | Poznan (Archdiocese) | 2004 | ap2005 |
| 4 | 1,470,100 | 1,580,000 | 93.04% | Wrocław {Breslavia} (Archdiocese) | 2004 | ap2005 |
| 5 | 1,460,000 | 1,540,000 | 94.81% | Łódż (Archdiocese) | 2004 | ap2005 |
| 6 | 1,438,200 | 1,533,000 | 93.82% | Warszawa {Warsaw} (Archdiocese) | 2004 | ap2005 |
| 7 | 1,128,115 | 1,134,319 | 99.45% | Tarnów | 2004 | ap2005 |
| 8 | 1,099,830 | 1,150,063 | 95.63% | Zielona Góra-Gorzów | 2004 | ap2005 |
| 9 | 1,092,000 | 1,135,000 | 96.21% | Warszawa-Praga | 2004 | ap2005 |
| 10 | 1,070,000 | 1,097,570 | 97.49% | Lublin (Archdiocese) | 2004 | ap2005 |
| 11 | 1,000,000 | 1,074,000 | 93.11% | Szczecin-Kamien (Archdiocese) | 2004 | ap2005 |
| 12 | 996,962 | 1,015,903 | 98.14% | Gniezno (Archdiocese) | 2004 | ap2005 |
| 13 | 983,840 | 1,051,984 | 93.52% | Legnica | 2003 | ap2004 |
| 14 | 923,195 | 977,614 | 94.43% | Gdansk (Archdiocese) | 2004 | ap2005 |
| 15 | 915,708 | 935,500 | 97.88% | Radom | 2004 | ap2005 |
| 16 | 890,000 | 965,000 | 92.23% | Koszalin-Kołobrzeg | 2004 | ap2005 |
| 17 | 860,000 | 900,000 | 95.56% | Opole | 2004 | ap2005 |
| 18 | 839,694 | 859,725 | 97.67% | Włocławek | 2004 | ap2005 |
| 19 | 826,885 | 867,315 | 95.34% | Czestochowa (Archdiocese) | 2004 | ap2005 |
| 20 | 802,000 | 850,000 | 94.35% | Pelplin | 2004 | ap2005 |
| 21 | 800,500 | 811,000 | 98.71% | Sosnowiec | 2004 | ap2005 |
| 22 | 777,000 | 806,800 | 96.31% | Płock | 2004 | ap2005 |
| 23 | 763,352 | 780,000 | 97.87% | Przemysl (Archdiocese) | 2004 | ap2005 |
| 24 | 761,510 | 785,248 | 96.98% | Kielce | 2004 | ap2005 |
| 25 | 758,300 | 768,700 | 98.65% | Kalisz | 2004 | ap2005 |
| 26 | 741,185 | 752,692 | 98.47% | Siedlce | 2004 | ap2005 |
| 27 | 730,500 | 807,000 | 90.52% | Biełsko-Zywiec | 2004 | ap2005 |
| 28 | 707,270 | 727,495 | 97.22% | Sandomierz | 2004 | ap2005 |
| 29 | 693,000 | 710,000 | 97.61% | Warmia (Archdiocese) | 2004 | ap2005 |
| 30 | 667,796 | 731,933 | 91.24% | Gliwice | 2004 | ap2005 |
| 31 | 653,140 | 687,514 | 95.00% | Swidnica | 2004 | ap2005 |
| 32 | 608,311 | 636,862 | 95.52% | Torun | 2004 | ap2005 |
| 33 | 604,354 | 606,414 | 99.66% | Łowicz | 2004 | ap2005 |
| 34 | 600,699 | 612,832 | 98.02% | Rzeszów | 2004 | ap2005 |
| 35 | 567,035 | 573,647 | 98.85% | Łomża | 2004 | ap2005 |
| 36 | 484,585 | 486,909 | 99.52% | Zamosc-Lubaczów | 2004 | ap2005 |
| 37 | 460,000 | 480,000 | 95.83% | Elbląg | 2004 | ap2005 |
| 38 | 425,000 | 440,000 | 96.59% | Ełk | 2004 | ap2005 |
| 39 | 370,450 | 434,826 | 85.19% | Białystok (Archdiocese) | 2004 | ap2005 |
| 40 | 206,000 | 292,000 | 70.55% | Drohiczyn | 2004 | ap2005 |
| 41 | 50,000 | Wrocław-Gdańsk (Ukrainian) | 2004 | ap2005 | ||
| 42 | 32,000 | Przemysl-Warszawa {-Warsaw} (Ukrainian) (Archdiocese) | 2004 | ap2005 |
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