Police forced their way into a house, in Ruislip, yesterday and found the bodies.
They said the cause of the deaths is “unexplained”.
A Metropolitan Police spokesman said officers headed to the home on The Fairway around 11am on Wednesday after concerns were raised.
“Officers found the bodies of a woman in her mid 30s and a 7-year-old boy”
Metropolitan Police spokesman
He said: “Inside officers found the bodies of a woman in her mid 30s and a 7-year-old boy.
“Police believe they know the identity of those concerned and are in the process of informing next of kin; formal identification awaits.”
Homicide and Major Crime Command detectives are investigating.
A post-mortem examination will be carried out at the Fulham Mortuary tomorrow.