18–
Kody w prefiksie 18–
42 kodów
| Kod | Miasto | Adr. | Ulic |
|---|---|---|---|
| 18-100 | Łapy | 4 777 | 163 |
| 18-105 | Suraż | 998 | 24 |
| 18-106 | Niewodnica Kościelna | 2 844 | 103 |
| 18-112 | Gąsówka Stara | 1 464 | 11 |
| 18-130 | Stopnica | 5 | 2 |
| 18-200 | Wysokie Mazowieckie | 3 387 | 85 |
| 18-204 | Kobylin-Borzymy | 822 | 7 |
| 18-205 | Jabłonka Kościelna | 1 | 1 |
| 18-208 | Kulesze Kościelne | 860 | 13 |
| 18-210 | Szepietowo | 1 964 | 39 |
| 18-212 | Jabłoń Kościelna | 1 221 | 16 |
| 18-214 | Klukowo | 1 282 | 8 |
| 18-218 | Sokoły | 1 841 | 31 |
| 18-220 | Czyżew | 132 | 30 |
| 18-225 | Pupki | 1 | 1 |
| 18-230 | Ciechanowiec | 257 | 40 |
| 18-232 | Granne | 1 | 1 |
| 18-300 | Zambrów | 4 874 | 100 |
| 18-301 | Zambrów | 1 | 1 |
| 18-305 | Szumowo | 1 437 | 15 |
| 18-312 | Rutki-Kossaki | 1 410 | 22 |
| 18-315 | Kołaki Kościelne | 697 | 11 |
| 18-400 | Łomża | 10 665 | 315 |
| 18-402 | Łomża | 5 | 3 |
| 18-403 | Łomża | 2 | 2 |
| 18-404 | Łomża | 2 | 2 |
| 18-411 | Śniadowo | 1 722 | 19 |
| 18-413 | Rydzewo | 979 | 37 |
| 18-414 | Nowogród | 1 349 | 60 |
| 18-416 | Zbójna | 1 738 | 35 |
| 18-417 | Kuzie | 1 | 1 |
| 18-420 | Jedwabne | 30 | 10 |
| 18-421 | Piątnica Poduchowna | 3 169 | 47 |
| 18-423 | Przytuły | 588 | 8 |
| 18-430 | Wizna | 1 319 | 31 |
| 18-500 | Kolno | 3 834 | 88 |
| 18-501 | Wrocław | 2 | 1 |
| 18-505 | Lachowo | 2 | 1 |
| 18-507 | Grabowo | 844 | 12 |
| 18-516 | Mały Płock | 1 104 | 19 |
| 18-520 | Stawiski | 197 | 24 |
| 18-525 | Turośl | 1 382 | 21 |