There are four types of taxis operating in Seoul, depending on their use and technology :  Regular taxis, deluxe taxis, high-tech brand taxis, and jumbo taxis.

Regular taxis are good and the drivers speak English quite well.

Deluxe taxis are painted black and yellow and offer a superb level of service, at a higher price of course.

High-tech brand taxis come with GPS (Global Positioning Systems) and are, as per the name, high tech.

Jumbo taxis are eight-seaters that are great for those travelling with excess luggage or for those  travelling in groups.

Deluxe Taxis
Telephone: (02) 3431 5100
Kind Call Taxi (Brand Taxi Service)
Telephone: (02) 1588 3382
KT Powertel (Brand Taxi Service)
Telephone: (02) 1588 0082
Jumbo Taxis
Telephone: (02) 888 2000