Virgin Media customers in Tayside and Fife were left without internet or television.
Hundreds of reports of outages were made on Wednesday, according to Down Detector.
Another website, which is not run by Virgin, said the fault mostly affected TV and Internet but some reports of phone problems were also made.
Swathes of Dundee, Perth, Glenrothes, Dunfermline and Kirkcaldy were among many areas across Scotland that experienced problems.
Where has been affected?
In Dundee, issues were reported in DD1, DD2, DD3, DD4 and DD5.
PH1 and PH2 postcodes in Perth were also affected, as well as Glenrothes, Kirkcaldy and Dunfermline in Fife.
The worst-hit postcodes in Fife were KY1, KY2, KY6, KY7, KY11 and KY12.
A spokeswoman for Virgin Media said only Perth was affected in a brief outage but a website that reports service problems also showed issues in Dundee.
Various parts of Fife were also affected.
The Virgin Media spokeswoman said: “There was an issue earlier on Wednesday that briefly affected broadband services for a very small number of customers in the Perth area.
“The issue was quickly resolved, and we apologise for any inconvenience caused.”