The leaders of the UK, Germany, France and Italy were expected to press Vladimir Putin to do more to end the fighting.
Italian PM Matteo Renzi said after the talks he was “more positive” on prospects for a solution to the crisis.
The West accuses Russia of arming separatist rebels and sending regular troops to Ukraine. Moscow denies this.
Ukraine and the rebels agreed a truce in September, but each side accuses the other of repeated shelling.
The separatists control parts of Ukraine’s Donetsk and Luhansk regions.
More than 3,600 people have been killed since the fighting erupted in April, following the annexation by Russia of Ukraine’s southern Crimea peninsular a month earlier.
Vladimir Putin, Petro Poroshenko and EU leaders met on the sidelines of the Asia-Europe (ASEM) summit in the northern Italian city.
The other participants in the meeting included UK Prime Minister David Cameron, French President Francois Hollande, German Chancellor Angela Merkel and Matteo Renzi.
Speaking briefly after the talks, the Italian prime minister said they were constructive but big differences remained.
“I’m more positive, I hope we can work together very strongly,” he told journalists.
Petro Poroshenko met Angela Merkel ahead of Friday’s talks, with both expressing regret that many points of a peace plan agreed last month in the Belarusian capital Minsk “had not yet been implemented”, German government sources were quoted as saying by the AFP news agency.
Angela Merkel also met Vladimir Putin for two-and-a-half hours late on Thursday, October 16.
Russian media quoted Kremlin spokesman Dmitry Peskov as saying that there were still “serious differences” between the two leaders over the origins of the crisis.
Angela Merkel said it was “first and foremost” Russia’s responsibility to make sure the peace plan was being followed.
Among other points, the plan envisages the withdrawal of heavy weaponry 10 miles by each side from the line of contact and the withdrawal of all foreign mercenaries from the conflict zone.
Earlier this week, Vladimir Putin ordered the withdrawal of nearly 18,000 Russian troops stationed near the Ukrainian border.
However, NATO says it has seen no sign of any major Russian pullback.
Speaking ahead of the Milan talks, Vladimir Putin stressed that he would not be blackmailed by the EU and US over the Ukrainian crisis.
In what was seen as a direct reference to President Barack Obama, the Russian leader warned of “what discord between large nuclear powers can do to strategic stability”.
The two-day ASEM summit brings together more than 50 member states.
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