How can I do this?

If I run an on demand scan the logfile produced is huge and takes a long time to look through. Is there any way I can set nod32 to just log threats rather than everything?

 

Perhaps you have configure NOD32 to "Log all files" .
Without this option , ESET NOD32 will log only threats and protected files that cannot be accessed

Open the on-demand scanner profiles -> "Setup" tab and make your settings look like that:

 

Yes I had enabled list all files, however that was a one off occasion and logged 4 threats. Without that enabled no threats were found. I'm confused.

 

Perhaps when the first time "List all files" was enabled , the threats have been eliminated . The next time nothing was found because all the malware has previously been killed

 

Yes I think you are correct there as I get no reports of threats in subsequent scans I tried.
Still annoyed that I couldn't find them to see what they were though.