Imaginary friends are very common among children between 3 to 7 years old and usually not a problem – as long as they don't interfere with carrying on normal life. It's best not to try to talk kids out of them, but to inquire about what the friend is thinking and doing. Imaginary friends give parents a great window into what kids are thinking. Imaginary friends are a sign of creativity; they are not a signal of loneliness or stress. You don't want to dwell on the friend, but from time to time joining your son in the imagination is great. Imaginary friends usually disappear within 6 months, whether or not you encourage them.