All postcodes in LL55 9
| Postcode | Place | Type |
|---|---|---|
| LL55 9AQ | Caernarfon | large user |
| LL55 9BH | Caernarfon | large user |
| LL55 9BX | Caernarfon | large user |
| LL55 9DA | Caernarfon | large user |
| LL55 9DD | Caernarfon | large user |
| LL55 9DE | Caernarfon | large user |
| LL55 9ZX | Caernarfon | large user |
| LL55 9ZZ | — | large user |