"These are our military and civilians," Ukrainian President Volodymyr Zelenskiy wrote on X.
He said many of the Ukrainian POWs had severe injuries and illnesses and would receive medical care.
Russia's defence ministry said the two sides had swapped 25 prisoners each.
The Russian POWs were in Belarus receiving medical and psychological support.
"All released servicemen will be transported to the Russian Federation for treatment and rehabilitation in medical institutions of the Russian Ministry of Defence," it said.
According to the statement, the exchange took place on the border with Belarus.
Zelenskiy thanked the UAE, which has brokered similar swaps before, for its assistance "in making today's event possible".
Ukraine's co-ordination centre for POW affairs said the youngest freed prisoner was 24 while the oldest was 60.
"The wounded are suffering from injuries, including loss of vision, limb amputations, complex bullet wounds and the consequences of explosion-related injuries," the centre said in a statement on Telegram.
Ukraine has been resisting the Russian invasion for almost three years.
Zelenskiy said Russia launched scores of missiles and drones at Ukraine on Wednesday, targeting gas infrastructure and other energy facilities in western regions in a new barrage against the power system in the depths of winter.
Ukrainian officials said the Russian forces launched more than 40 missiles during the morning attack and used more than 70 drones overnight.
Ukrainian air defences shot down 30 missiles and 47 drones, the air force said.
Another 27 drones were "lost" in reference to Ukraine using electronic warfare to redirect them.
"Another massive Russian attack. It's the middle of winter, and the target for the Russians remains unchanged: our energy infrastructure," Zelenskiy said in a social media post on X platform.
"Among their objectives were gas and energy facilities that sustain normal life for our people."
with DPA
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