The best period to visit Ukraine and Kiev is May - the month when chesnut trees and lilac in blossoming :)
Must have to visit in Kiev: Lavra, St. Sofia Cathedral, Abdrew descent, Golden Gate, walking by main street Kreschatic, boat-trip by Dnipro (if you have only 1 day to spend in capital of Ukraine).
Kiev is a lovely city where it is quite difficult to be bored. However, you have to know places to go. So let me give you some tips: There are great restaurants in Kiev such as Amici Mi (intenational), Safe (Intenational), Porto (Mediterranian, Fish), Velour (European, Japanese), Budda Bar (Fusion), Belveder (International), Da Vinci (Italian,Fish), Ribna Bazaar (Fish), OK Bar (Fusion, International), Concord (European, Fusion), Just Cafe (Japanese, International), Murakami (Japanese,...
I would love to visit both Ukraine and Russia. Could someone recommend some interesting places to stay in both countries. I am interested in Kiev, Crimea , Yalta , St. Petersburg, Moscow etc. I would like to spend about a week in Kiev . Same amount of time in St. Petersburg and Moscow