The incident, which began on 25 November, saw the trust isolate its systems as a precaution to ensure that the problem did not spread.
A Wirral University Teaching Hospital spokesperson said: ‘We are currently in the process of reinstating our main clinical system following the cyber security incident last week. As we work through our recovery the incident will be stepped down to a Business Continuity Incident.
‘Some services will continue to be affected this week as systems are restored.'
The trust advised anyone with an outpatients appointment to attend their appointment.
Emergency treatment is being prioritised, but there are still likely to be longer than usual waiting times, the trust added.