If the country was divided into several parts, the special code HH is used to indicate that there is no single successor country (e.g., Czechoslovakia was divided into the Czech Republic and Slovakia), with the exception of Serbia and Montenegro, for which XX is used to avoid duplicate use of the same ISO 3166-3 code, as the alpha-2 code CS had twice been deleted from ISO 3166-1, the first time due to the split of Czechoslovakia and the second time due to the split of Serbia and Montenegro.
Hvis landet er blev delt i flere dele, bruges specialkoden HH for at indikere, at der ikke findes et efterfølgerland (f.eks. da Tjekkoslovakiet blev opdelt i Tjekkiet og Slovakiet), med undtagelse af Serbien og Montenegro, hvor man bruger XX for at undgå at samme ISO 3166-3-kode bliver brugt to gange, eftersom koden CS er blevet slettet fra ISO 3166-1 to gange.