There is a visa regime in Ukraine
You don’t need a visa for tourist trips not exceeding 90 days, if you are a citizen of European Union, USA, Canada, Japan, Switzerland, Liechtenstein, Andorra, Vatican, Monaco, Iceland, Norway, San-Marino, Mongolia, Serbia, Montenegro, The Commonwealth of Independent States (except Turkmenistan).
The detailed information on an order of entrance to Ukraine can be received in a consular institution of Ukraine abroad.
Citizens from countries which has concluded international agreements on mutual visa-free travel with Ukraine, move in Ukraine under the valid International passport. They need to have properly issued invitations from individuals or legal entities in Ukraine, unless otherwise stipulated by international treaties of Ukraine. More information on the entry to the couyntry can be obtained at the consular establishments of Ukraine abroad.
Citizens of other countries can get visas within several hours - after visiting the Ukrainian Consulate and having received 'the invitation'. The additional information is available at the the Ukrainian Embassy in your country.
Always know how much currency you have. As customs officials should be aware of the amount of money entering the country.
Norms and rules are supposed to change in short terms without wide announcement. That’s why it’s better to check up beforehand the existing customs rules (e.g. Web-site of airport Boryspil)
For entry you need to fill out an immigration form. It consists of two rather simple documents, containing almost identical information. Both parts must be certified on arrival. One part is at the Immigration officer, the other with you. You need to show it to immigration officers when you move off the country. Do not lose it for not have difficulties on leaving the country (a fine is the possible for a loss).
It is recommended to know the place of stay, as this information is to fill in the immigration form.