Old:

format - 00 000-00aa

usual: symbol - black, background - white
bus,taxi: symbol - black, background - yellow
transit: symbol - black, background - green
police:
format - 00 0000aa
symbol - white, background - blue

region - first two figures or first letter:

01 - Republic of Crimea
02 - Vinnytsia region
03 - Volyn region
04 - Dnepropetrovsk region
05 - Donetsk region
06 - Zhitomyr region
07 - Zakarpatye region
08 - Zaporozhie region
09 - Ivano-Frankivsk region
10 - Kiev region
11 - Kiev
12 - Kirovograd region
13 - Lugansk region
14 - Lviv region
15 - Nykolaev region
16 - Odessa region
17 - Poltava region
18 - Rovno region
19 - Sumy region
20 - Ternopil region
21 - Kharkov region
22 - Kherson region
23 - Khmelnytsky region
24 - Cherkasy region
25 - Chernigov region
26 - Chernivtsi region
27 - Sevastopol

New(since 2004):

format - aa 0000 aa

usual: symbol - black, background - white
bus,taxi: symbol - black, background - yellow

region - first two letter:

II - nation
AK - Republic of Crimea
AB - Vinnytsia region
AC - Volyn region
AE - Dnepropetrovsk region
AH - Donetsk region
AM - Zhitomyr region
AO - Zakarpatye region
AP - Zaporozhie region
AT - Ivano-Frankivsk region
AI - Kiev region
AA - Kiev
BA - Kirovograd region
BB - Lugansk region
BC - Lviv region
BE - Nykolaev region
BH - Odessa region
BI - Poltava region
BK - Rovno region
BM - Sumy region
BO - Ternopil region
AX - Kharkov region
BT - Kherson region
BX - Khmelnytsky region
CA - Cherkasy region
CB - Chernigov region
CE - Chernivtsi region
CH - Sevastopol

transit:
format - 0000 aa
symbol - black, background - red

army:
format - 0000 a0
symbol - white, background - black

diplomatic:
format - D 000 000
symbol - black, background - white

Ukraine
Embassies and Consulates
Road distance
Photo from Ukraine