| Document And Entity Information | Mar. 21, 2022 |
| Document Information [Line Items] | |
| Entity, Registrant Name | DIFFUSION PHARMACEUTICALS INC. |
| Document, Type | 8-K |
| Document, Period End Date | Mar. 21, 2022 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 000-24477 |
| Entity, Tax Identification Number | 30-0645032 |
| Entity, Address, Address Line One | 300 East Main Street, Suite 201 |
| Entity, Address, City or Town | Charlottesville |
| Entity, Address, State or Province | VA |
| Entity, Address, Postal Zip Code | 22902 |
| City Area Code | 434 |
| Local Phone Number | 220-0718 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | DFFN |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001053691 |
