NHS Trusts that run hospitals in Southport, Ormskirk, Chorley and Preston have cancelled or postponed surgery scheduled for today.
People living in Lancashire South Cumbria have also been warned to expect some disruption to GP services as IT and clinical systems are brought back online.
Hundreds of operations and appointments had to be cancelled following Friday's security breach, which saw total of 48 NHS trusts in England affected when a ransomware virus infiltrated dozens of NHS organisations.
Security experts have warned that further cyber attacks on the NHS and other organisations are imminent.
Experts believe it's possible that more hospitals could be affected this week.