The trust in charge of Watford General Hospital will only get money from the health campus if it sells part of its site.
Samantha Jones, chief executive of West Hertfordshire Hospitals NHS Trust, said the regeneration scheme was giving the hospital land "flexibility" to redevelop.
However the method of funding for any large scale redevelopment of Watford General Hospital would only be decided after the trust finished drawing up its strategy for the future.
It also emerged this week that the trust is not a part of the health campus legal agreement between Watford Borough Council and developers Kier, but it retains a veto over the proposals.
In an interview with the Watford Observer, Ms Jones said the trust was currently working on its clinical strategy, which would determine hospital services in Watford, St Albans and Hemel Hempstead for the coming decades.
She said: "I am on record as saying our buildings are not fit for purpose and I don’t think anybody would disagree with me.
"The question people want the answer to is ‘what is the future of the clinical services and what is the future of Watford, St Albans and Hemel’. And we have said that, with our commissioners, because we have to respond to what our commissioners want.
"We are reviewing how those services are provided by us but also by the community services and also by the mental health trust and the primary care, to see what does the future of healthcare look like in west Hertfordshire.
"And that is important and that is completely relevant to the health campus, because we need to make sure that whatever we have here is fit for the next five years and the next 20 years."
The health campus project plans to redevelop the land around the hospital, behind Vicarage Road, with around 700 new homes as well as business and green spaces. Part of the scheme has been earmarked for the hospital’s redevelopment.
This week the trust confirmed that it would only receive money from the scheme if it sold some of its land to the developers. However the trust said the health campus had already financially benefited the hospital as it had helped it to secure funding for the new access road from Dalton Way.
The shape of the new hospital services will not become clear until the clinical strategy is finalised, which could be as late as mid 2015. The trust has already confirmed that the A&E and maternity until will be staying in Watford, but little else has been divulged.
Ms Jones added that part of the reason the clinical strategy was taking a long time was that the management had changed at the hospital since she took the helm last year.
She also said the last couple of years had seen sweeping NHS reforms that meant hospital services were heavily influenced by what GP-run consortiums wanted.
Ms Jones said: "Yes the landscape in the NHS has completely changed and there was a new landscape from April 2013 when the CCGs (clinical commissioning groups) came in and took responsibility. But healthcare has to be provided and with the questions we’re working through with our commissioners, and we have a really good relationship with our commissioners at Herts Valley CCG."