The Cardiff and Vale University Health Board says two wards, Ocean and Land, are open to patients and it hopes Sky ward will be open tomorrow. The final patient area, Space, should reopen next week.
Directorate Manager for Child Health, Phil Barry:
"We want to thank all our staff for their fantastic work."
Patients were transferred to the main building after torrential downpours damaged the building. Specialist drainage consultants have been brought in to investigate.
Patients are expected to be moved back into parts of Wales' only children’s hospital by Thursday.
The Noah's Ark Children's Hospital for Wales was closed because of water damage yesterday due to torrential rain earlier in the week.
Eighteen children in total were moved to other child health areas.
Phil Barry, Directorate Manager for Child Health, said: “All the staff involved have been fantastic. Our priority has been to provide an environment and safe care to all those affected by the incident."
Work to determine the exact cause and to asses the extent of the damage to the higher floors will continue over the next few days.
Wales' only children's hospital has been evacuated after heavy rain caused significant flooding.
18 patients had to move after water left parts of the Noah's Ark Children's Hospital unsafe.
Patients are expected to move back into parts of the unit in Cardiff within 36 hours.
Health bosses are now investigating how a relatively new building was damaged by rainfall.
Patients are expected to be moved back into parts of the Children's Hospital for Wales within the next 36 hours.
Work to determine the cause of flooding yesterday, and to assess the extent of damage to upper floors, where water has been found in the electrical trunking systems and light fittings, will be continuing over the next few days.
Cardiff and Vale University Health Board says services at the hospital have remained in place, and has advised patientsand their families to come to the hospital as normal, unless they are told otherwise.
Dr George Findlay, Cardiff and Vale University Health Board's Clinical Board Director for Children and Women, told ITV News that between six and 12 inches of water had flooded the top two floors of the Children's Hospital for Wales - and some ceiling tiles had come down with the force of the water.
Cardiff and Vale University Health Board said that "torrential rain" yesterday caused water to enter the Children's Hospital for Wales.
The hospital has been "temporarily evacuated" while the extent of water damage is assessed.
It says 18 patients have been safely moved to child health areas in the main University Hospital of Wales building, and are being cared for by staff from the children's hospital.
Paediatric emergency and elective inpatient services have not been affected.
The cause of the flooding is currently being investigated.
The Children's Hospital for Wales in Cardiff has been closed due to damage caused by heavy rainfall.
18 children being treated there have been moved to other wards at the University Hospital of Wales.
The hospital was closed and patients moved on Monday afternoon.
Nobody was injured.
Cardiff and Vale University Health Board says it doesn't expect the hospital to reopen before the end of the week, as damage to electrics is examined.
An art exhibition by young patients depicting their experiences of hospital has been described as 'eye-opening' by staff working in the health sector.
Children's Commissioner Keith Towler will today visit Noah's Ark Children's Hospital for Wales to unveil an art exhibition depicting young patients' experiences of hospital.
The youngsters have worked alongside artists from Valley and Vale Community Arts for the project, which is funded by the Arts Council of Wales.
Many patients have long-term conditions which make them frequent visitors to the children's hospital.
Through the project, they turned to paint and pencils to share their their emotions as they went through treatment.
Linda Hughes-Jones, who works for Cardiff and Vale University Health Board and also led the project, said the artwork is 'eye-opening' and has given health workers 'a different perspective' on how it feels to be a young person in hospital.
The artwork will be displayed on the hospital walls, as well as appearing in a short DVD.
Schoolchildren have unveiled the names and designs they have chosen for the new areas of the Children's Hospital for Wales. Building work to extend the current site is underway, and when it's finished, the hospital is expected to treat around a 100,000 young people every year. Esyllt Carr reports.