mental picture vs impression

mental picture and impression both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental picture	Yes	No	No	No
impression	Yes	No	No	No

As nouns, mental picture and impression are synonyms defined as:

Other synonyms of mental picture include picture.

mental picture (noun)	impression (noun)
a clear and telling mental image	an impressionistic portrayal of a person
	the act of pressing one thing on or into the surface of another
	(dentistry) an imprint of the teeth and gums in wax or plaster
	an outward appearance
	a vague idea in which some confidence is placed
	a clear and telling mental image
	a symbol that is the result of printing or engraving
	all the copies of a work printed at one time
	a concavity in a surface produced by pressing