Travel to Ukraine
ENTRY / EXIT REQUIREMENTS FOR U.S. CITIZENS: You need a valid passport to enter Ukraine. If you are a U.S. citizen, you do not need to have a Ukrainian visa as long as you will be in Ukraine for fewer than 90 days within a 180-day period. You need a visa or valid Ukrainian residency permit for all stays longer than 90 days. You cannot get a Ukrainian visa at the airport or at the border. If you need a visa, please get it in advance at a Ukrainian Embassy or Consulate. Contact information for Ukrainian Embassies and Consulates outside of the United States is available on the Ukrainian Ministry of Foreign Affairs website. [1]
google: USA and Ukraine citizenship, how to travel with two passports when duel citizenship isn't allowed by Ukraine?
A: Every person (including children of any age) requires a visa to travel to the U.S. You will need to fill out the application form DS-160 online for your child and pay the $160 visa application fee. If your child’s visa is approved, that visa will be placed in your passport. Please note, for all cases involving children under 16, both parents should be present at the interview. For detailed information on our nonimmigrant visa application procedures please visit our website at: http://ukraine.usembassy.gov/. [2]