North-western Cambodia is a region of Cambodia and includes the provinces of Banteay Meanchey, Oddar Meanchey, Preah Vihear, Siem Reap and the part of Stoeng Treng to the west of the Mekong.
The north is dominated by the Dangrek Mountains which form the natural barrier between Cambodia and Thailand. Much of the southern part of this region is very flat and fertile leading towards the Tonle Sap - Cambodia's great lake.
Siem Reap is by far the largest city, Sisophon and Poipet both small towns, while Anlong Veng just feels like a large village.
Much of north-western Cambodia live in abject poverty, with the province of Siem Reap being one of the poorest in the country, despite the valuable Angkor Archaeological Park being located within. Like the other regions, infrastructure is a new concept in North-Western Cambodia, with only the national highways paved. Out of the towns, electricity is obtained by using car batteries, at a high cost. Despite the obvious negative effects that a lack of development can have, an advantage (if there was one) would be that the region has been largely left alone by tourists, so those who do tread off the tourist trail get an insight into Cambodia's beautiful struggle.
The region is served by Siem Reap - Angkor International Airport  (IATA: REP | ICAO: VDSR) which has has frequent domestic flights from Phnom Penh and is internationally linked from the following destinations:
If you're only making your way between towns in the region, then the days of rough, impassable roads and adventure are over. Most main routes are now paved, with the exception of only a few.
There are a range of bus companies serving all towns large enough to be worth visiting. The larger the town, the more regular the service.
Where the bus companies don't go, one should usually be able to travel by taxi. For the best chance of success, organize your taxi the night before, otherwise an early start may be needed to secure a place in a share-taxi.
By Pick-up Truck
It's not as simple to organize a pick-up truck as it is a taxi, but they have a different market - budget outside tickets. Used for passengers and cargo, pick-up trucks head everywhere, providing a broad network, linking most every lonely village. If it wasn't for these banged up wagons, most of the region wouldn't have access to affordable transport. Simply stand on the edge of the road, and flag the first one down.
By Kuyon (tractor)
For those outside town trying to cover a distance of 15km or so, hitching a ride on a local tractor can be as simple as flagging the first one down. Be aware that this is, effectively, hitch hiking, and comes with the usual dangers. USD$0.75 per 15km would be appropriate.
North Western Cambodia is home to the infamous K5 mine belt, a (land) mine field 700km long and 500m wide, that runs parallel to the border with Thailand. Although parts of this minefield have been cleared, much remains. When travelling in remote areas, never stray too far off the road or track, it's just not worth the risk.
Three of Cambodia's six overland crossings with Thailand are in this region: