Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 05, 2020
Document Information [Line Items]
Entity Registrant Name	Diffusion Pharmaceuticals Inc.
Entity Central Index Key	0001053691
Trading Symbol	dffn
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Current Reporting Status	Yes
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding (in shares)		63,998,298
Entity Shell Company	false
Document Type	10-Q
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false
Title of 12(b) Security	Common Stock, par value $0.001 per share