Geographical area codes start with the digit 2. There are currently two-, three-, and four-digit area codes. The only two-digit area code is 21 for the Athens Metropolitan area: three-digit codes are used for the cities Thessaloniki, Patras, Larissa, Heraklion, Kavala, Tripoli. The rest of the codes are four-digit codes.

Generally speaking, the second digit of a geographical area code signifies a broader geographical area of Greece, That is how area codes are sorted in this article.

Two-digit codes are used with eight-digit subscriber numbers, three-digit codes with seven-digit numbers, and four-digit codes with six-digit numbers so the full telephone number is always ten digits.

Subscriber numbers in most areas start with 0. That is the digit that was inserted between the area code and the subscriber number in order to form the new ten-digit numbering plan back in 2002. Thus, many Greeks erroneously think that the area codes include this leading 0. For example, they think that Athens's area code is 210 while, actually, Athens's area code is 21, 0 being the first digit of the subscriber number.

Subscriber numbers starting with 0 are assigned to the former monopoly OTE. In bigger cities like Athens and Thessaloniki, subscriber numbers starting with other digits except 0 are becoming more and more common, especially amongst business subscribers. In this case many people think that the area code is different. For example, a subscriber number in Athens might start with 211, with people thinking that 211 is a distinct area code from 210 while, in reality, both numbers are in the 21 area code and the third digit of the number belongs to the subscriber number.

The international call prefix depends on the country from which you are calling, for example, 00 for most European countries and 011 from North America.

 xxx xxxx (within Athens)
 (01) xxx xxxx (within Greece)
 +30 1 xxx xxxx (outside Greece)

In 2001, a '0' was added after the area code, which was incorporated into the subscriber's number:

 01 0xxx xxxx (within Greece, including Athens)
 +30 1 0xxx xxxx (outside Greece)

Finally, in 2002, the leading '0' was changed to a '2' (for geographic numbers) :

 21 0xxx xxxx (within Greece, including Athens)
 +30 21 0xxx xxxx (outside Greece)

Mobile phone numbers were similarly prefixed with the digit '6'.

Note that because of number portability, for both geographical and non-geographical (mobile, toll-free, premium rate) numbers, one cannot be sure about the operator that a number belongs to. Thus, for geographical numbers, one cannot be sure that a subscriber number that starts with a 0 is operated by OTE or that a toll free number that starts with 800-11 is operated by OTE. Also for mobile networks one cannot say for sure that a number that starts with a 69x actually belongs to the mobile carrier to which it was assigned.

234x and 236x are not used.