Consuming WCF service in MVVM application

I am consuming a WCF service in my MVVM application....

I am currently using 1 DTO as the model in my MVVM but I am also calling the WCF service multiple times from within the 1 ViewModel (That return other DTOs) to populate a bunch of drop down lists. Is this perfectly valid? Or should the WCF service be returning a ViewModel that contains everything the View needs?