Russian President Vladimir Putin and his Ukrainian counterpart Petro Poroshenko discussed a possible exchange of prisoners during a telephone call on Saturday.
Poroshenko had placed particular emphasis on the situation of Ukrainian citizens being held in Russia who are on hunger strike, the president's office said in a statement.
Relations between Moscow and Kiev have been tense since 2014 when a popular uprising drove a pro-Russian president from power. Russia went on to annex Crimea from Ukraine and backed a pro-Russian separatist insurgency in the country's east.
The Kremlin said Saturday's call was initiated by Ukraine, adding that "particular attention is paid to issues of a humanitarian nature, including the exchange of detainees".
Ukraine says that at least 64 Ukrainians are 'political prisoners' in Russia, including 40 who are held in Crimea.
Kiev has repeatedly said that the release of its prisoners is a priority and the issue will be discussed during a planned meeting of foreign ministers on June 11.
"The first question apart from the deployment of peacekeeping mission, ceasefire and implementation of the Minsk agreement, is the issue of hostages," Poroshenko said on Friday, adding that Kiev had coordinated with France and Germany.
A Russian court sentenced a Ukrainian journalist, Roman Sushchenko, to 12 years in a maximum security prison last week after convicting him of spying.
And Ukrainian film director Oleg Sentsov is serving 20 years in jail in Russia for planning "terrorist attacks" in Crimea.