Residents in a quiet area of Blantyre, in South Lanarkshire, heard screams when the mum of one of the lads returned home to the grim discovery.
Police were called to Murray Crescent shortly after 6pm yesterday after a 999 call was made.
It is understood one of the men who died was 21-year-old Dominic Patterson, who lived at the house, and that his 25-year-old friend Colin Campbell also died.
The housing estate is home to young families and parents were with their youngsters at a playpark next to the house when the bodies were found.
Police officers asked them to leave and the area was cordoned off.
Officers also taped off the house and a fleet of police cars were at the scene.
Paramedics were called, but there was nothing they could do to save the friends.
Officers are continuing their investigations today into the deaths which police say are "unexplained".
They are not being treated as suspicious.
A spokeswoman for Strathclyde Police said: "Around 6.10pm last night police were called to a report of two men being found dead in Murray Crescent.
"Inquiries are at an early stage and post mortem examinations will be carried out to establish the exact circumstances surrounding the deaths."
Neighbours were stunned by the tragedy.
One woman, who did not want to be named, said: "It was such a shock to hear about what had happened."
Residents close by said they heard the mum of one of the lads screaming hysterically and then the next thing police were at the scene. The woman added: "As a mum myself this is absolutely heart-breaking.
"I have been here for eight years and it is such a quiet area. Nothing ever happens here, people just get on with their lives."
Another woman said: "There was little ones playing in the park with their parents when this happened.
"No one could have imagined what had happened in the house. Police asked everyone to leave the playpark."