Ancestry in Western Suffolk
Data from the Census Bureau's 2008-2010 American Community Survey on how residents identified their ancestry when given a selection of choices. Some towns are not listed because the number of residents surveyed was too small. Also, because this information is based on surveys, there is a different margin of error for each statistic. A complete listing of those margins and of all the data from Long Island, including information from 45 communities with populations of 20,000 or more, is available on this PDF.
| Ancestry | Suffolk | Suffolk percent | Babylon | Babylon percent | Brookhaven | Brookhaven percent | Huntington | Huntington percent | Islip | Islip percent | Smithtown | Smithtown percent |
| Slovak | 2,091 | 0.1 | 382 | 0.2 | 804 | 0.2 | 288 | 0.1 | 306 | 0.1 | 129 | 0.1 |
| Swiss | 2,886 | 0.2 | 240 | 0.1 | 1,252 | 0.3 | 580 | 0.3 | 376 | 0.1 | 158 | 0.1 |
| Welsh | 3,744 | 0.3 | 606 | 0.3 | 992 | 0.2 | 594 | 0.3 | 394 | 0.1 | 197 | 0.2 |
| Danish | 3,971 | 0.3 | 413 | 0.2 | 1,150 | 0.2 | 894 | 0.4 | 880 | 0.3 | 335 | 0.3 |
| Arab | 5,522 | 0.4 | 699 | 0.3 | 1,279 | 0.3 | 1,547 | 0.8 | 1,331 | 0.4 | 514 | 0.4 |
| Lithuanian | 6,157 | 0.4 | 782 | 0.4 | 1,629 | 0.3 | 1,173 | 0.6 | 919 | 0.3 | 727 | 0.6 |
| French Canadian | 6,250 | 0.4 | 848 | 0.4 | 2,302 | 0.5 | 472 | 0.2 | 1,146 | 0.3 | 460 | 0.4 |
| Scotch-Irish | 6,299 | 0.4 | 421 | 0.2 | 2,110 | 0.4 | 798 | 0.4 | 964 | 0.3 | 1,152 | 1.0 |
| Ukrainian | 6,967 | 0.5 | 804 | 0.4 | 2,361 | 0.5 | 1,258 | 0.6 | 1,048 | 0.3 | 364 | 0.3 |
| Czech | 7,450 | 0.5 | 605 | 0.3 | 2,858 | 0.6 | 1,307 | 0.6 | 1,417 | 0.4 | 625 | 0.5 |
| Portuguese | 7,734 | 0.5 | 558 | 0.3 | 3,876 | 0.8 | 653 | 0.3 | 1,753 | 0.5 | 238 | 0.2 |
| Subsaharan African | 9,614 | 0.6 | 2,439 | 1.1 | 4,650 | 1.0 | 735 | 0.4 | 1,227 | 0.4 | 243 | 0.2 |
| Swedish | 12,528 | 0.8 | 1,189 | 0.6 | 3,623 | 0.8 | 2,267 | 1.1 | 1,968 | 0.6 | 1,298 | 1.1 |
| Hungarian | 12,790 | 0.9 | 1,202 | 0.6 | 4,505 | 0.9 | 2,695 | 1.3 | 2,236 | 0.7 | 1,120 | 1.0 |
| Dutch | 12,792 | 0.9 | 1,722 | 0.8 | 3,500 | 0.7 | 2,159 | 1.1 | 2,378 | 0.7 | 1,115 | 0.9 |
| Norwegian | 14,973 | 1.0 | 1,494 | 0.7 | 5,076 | 1.1 | 2,054 | 1.0 | 2,971 | 0.9 | 1,605 | 1.4 |
| Scottish | 15,993 | 1.1 | 1,723 | 0.8 | 5,384 | 1.1 | 2,149 | 1.1 | 2,140 | 0.6 | 1,636 | 1.4 |
| Greek | 17,790 | 1.2 | 1,751 | 0.8 | 5,061 | 1.0 | 3,083 | 1.5 | 3,322 | 1.0 | 2,839 | 2.4 |
| French (except Basque) | 26,330 | 1.8 | 3,126 | 1.5 | 8,690 | 1.8 | 2,895 | 1.4 | 5,273 | 1.6 | 2,695 | 2.3 |
| West Indian (exludes Hispanic origin groups) | 29,941 | 2.0 | 11,072 | 5.2 | 6,418 | 1.3 | 2,948 | 1.5 | 9,057 | 2.7 | 331 | 0.3 |
| American | 30,022 | 2.0 | 3,382 | 1.6 | 9,076 | 1.9 | 6,095 | 3.0 | 5,847 | 1.7 | 2,889 | 2.5 |
| Russian | 37,789 | 2.5 | 3,640 | 1.7 | 11,135 | 2.3 | 9,239 | 4.6 | 4,454 | 1.3 | 5,537 | 4.7 |
| English | 83,303 | 5.6 | 8,673 | 4.1 | 28,171 | 5.8 | 11,983 | 5.9 | 13,363 | 4.0 | 6,227 | 5.3 |
| Polish | 88,032 | 5.9 | 12,631 | 5.9 | 26,863 | 5.6 | 13,266 | 6.5 | 14,948 | 4.5 | 8,842 | 7.5 |
| German | 245,831 | 16.5 | 34,181 | 16.0 | 87,224 | 18.1 | 32,667 | 16.1 | 49,153 | 14.7 | 22,098 | 18.8 |
| Irish | 338,921 | 22.8 | 43,081 | 20.2 | 121,321 | 25.1 | 43,592 | 21.5 | 70,052 | 20.9 | 31,934 | 27.1 |
| Italian | 423,350 | 28.5 | 60,871 | 28.5 | 152,704 | 31.6 | 54,984 | 27.1 | 82,979 | 24.8 | 47,141 | 40.1 |