An 18-month-old boy who fell down a lift shaft has escaped unharmed after clinging to the side of the lift for 15 minutes as it continued to move up and down a building in Melbourne's southeast.

The boy's parents said he had been playing with friends outside when they noticed he was missing, said paramedic Warren Simpson.

The boy's father then heard his son screaming and crying in the lift shaft.

No one knows how the boy managed to climb in between the lift and the lift wall, about 8pm (AEDT) on Sunday.

Country Fire Authority (CFA) firefighters arrived at the three-storey apartment block on Thomas Street in Dandenong to find the boy hanging six metres above the ground.

"He had been holding on to something on the side of the lift and the lift had actually been going up and down a number of times," said Mr Simpson.

"His father had heard him crying at the top of the lift and at the bottom of the lift.

"(He went) up two floors and then back down again a number of times, from what the patient's father was telling us.

"He said his voice, you could hear it at the top of the shaft and then when the lift went down you could hear it down at the bottom before they could stop the lift from going up and down."

Firefighters made access through the lift's emergency man hole and made a human chain to get the boy out, a CFA spokeswoman said.

"Firefighters made a human chain passing the child up to the roof of the lift and then back down to the waiting arms of his father," she said.

Mr Simpson said the boy was trapped for up to 15 minutes until being rescued by firefighters.

He said the boy emerged from the lift shaft covered in grease and dust.

"His stomach and his back were covered in grease and dust from the shaft so it must have only been a very small area in there that he was in," he said.

"He'd been rubbing as he'd been going up and down, very fortunate that he didn't catch on anything.

"It would have been terrifying for him."

Mr Simpson said the boy was examined by paramedics and was taken to Dandenong Hospital for observation but suffered no injuries during the incident.

"When you hear that a child is trapped in a lift well crying and screaming, unfortunately, you do tend to think it could possibly be worse than what it is," he said.

"To have the outcome that we did was excellent.

"Mum and dad naturally were quite shaken up over the whole thing, but it was a good outcome."

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