Country Code +350
City codes not required. Land lines 5 or 6 digits.
From a correspondent: "Mobile phone numbers have 8 digits, ending in 000. This is due to Spain's refusal to recognize the 350 code, which has restricted Gibraltar to 30,000 telephone numbers accessible from Spain using the provincial code 9567. Calls to landlines in Spain require only the 9 digit number, without the code 0034, although this is used for mobiles."
International City Dialing Codes