Notional results for a UK general election on 5 May 2005 Elections contested by Plaid Cymru
A notional general election to the 54th Parliament of the United Kingdom with an electorate of 40,611,844, having 24,814,623 valid votes.
| Constituency | Electorate | Turnout | Votes | Vote share | Position |
| Vale of Glamorgan | 68,229 | 68.5% | 2,426 | 5.2% | 4th |
| Cardiff South and Penarth | 67,855 | 58.2% | 2,071 | 5.2% | 4th |
| Cardiff West | 64,587 | 58.2% | 4,855 | 12.9% | 4th |
| Cardiff North | 64,390 | 70.4% | 1,936 | 4.3% | 4th |
| Caerphilly | 64,120 | 56.5% | 6,565 | 18.1% | 2nd |
| Monmouth | 62,233 | 73.4% | 993 | 2.2% | 4th |
| Cardiff Central | 61,079 | 59.2% | 1,271 | 3.5% | 4th |
| Torfaen | 60,665 | 59.3% | 2,242 | 6.2% | 4th |
| Gower | 60,432 | 65.4% | 3,089 | 7.8% | 4th |
| Newport West | 60,303 | 59.3% | 1,278 | 3.6% | 4th |
| Alyn and Deeside | 59,441 | 59.7% | 1,320 | 3.7% | 4th |
| Swansea West | 58,363 | 56.7% | 2,150 | 6.5% | 4th |
| Swansea East | 57,502 | 53.6% | 2,129 | 6.9% | 4th |
| Neath | 57,278 | 62.5% | 6,125 | 17.1% | 2nd |
| Carmarthen West and South Pembrokeshire | 57,143 | 67.3% | 5,960 | 15.5% | 3rd |
| Bridgend | 57,046 | 59.7% | 2,350 | 6.9% | 4th |
| Islwyn | 56,225 | 60.2% | 4,213 | 12.4% | 2nd |
| Preseli Pembrokeshire | 56,001 | 70.0% | 4,895 | 12.5% | 4th |
| Clwyd West | 55,381 | 65.1% | 3,912 | 10.9% | 4th |
| Llanelli | 55,280 | 63.9% | 9,358 | 26.5% | 2nd |
| Brecon and Radnorshire | 55,171 | 69.5% | 1,404 | 3.7% | 4th |
| Newport East | 54,941 | 57.9% | 1,221 | 3.8% | 4th |
| Pontypridd | 54,122 | 63.2% | 3,757 | 11.0% | 4th |
| Merthyr Tydfil and Rhymney | 54,044 | 55.5% | 2,972 | 9.9% | 3rd |
| Ogmore | 53,842 | 59.5% | 3,274 | 10.2% | 4th |
| Delyn | 53,383 | 63.7% | 2,524 | 7.4% | 4th |
| Blaenau Gwent | 53,301 | 66.1% | 843 | 2.4% | 4th |
| Carmarthen East and Dinefwr | 52,741 | 70.8% | 17,124 | 45.9% | 1st |
| Ceredigion | 52,514 | 68.0% | 12,827 | 35.9% | 2nd |
| Ynys Môn | 52,512 | 67.5% | 11,036 | 31.1% | 2nd |
| Clwyd South | 51,201 | 61.2% | 2,958 | 9.4% | 4th |
| Aberavon | 50,685 | 59.4% | 3,545 | 11.8% | 3rd |
| Rhondda | 50,461 | 61.7% | 4,956 | 15.9% | 2nd |
| Vale of Clwyd | 49,637 | 65.8% | 2,346 | 7.2% | 4th |
| Dwyfor Meirionnydd | 48,823 | 61.4% | 15,228 | 50.8% | 1st |
| Cynon Valley | 48,272 | 60.2% | 3,939 | 13.5% | 2nd |
| Wrexham | 48,016 | 63.3% | 1,744 | 5.7% | 4th |
| Montgomeryshire | 46,655 | 66.3% | 2,156 | 7.0% | 4th |
| Aberconwy | 43,976 | 62.0% | 3,818 | 14.0% | 4th |
| Arfon | 42,998 | 58.2% | 8,028 | 32.1% | 2nd |
Turnout as calculated by the House of Commons Library, is the total number of votes cast and not spoiled, divided by the size of the electorate.
Under section 13(b) of the Representation of the People Act 1985, a candidate gaining 5% or less of the vote share will forfeit their deposit.
Estimates of the 2005 general election result in new constituencies
Professors Colin Rallings and Michael Thrasher, at The Elections Centre of the University of Exeter, produced estimates of the 2005 general election result as if the new constituencies recommended by the separate Parliamentary Boundary Commissions for England, Wales and Northern Ireland had then been in existence.