Primeramente definimos el tipo JSON a descargar

Public Class Nodo
    Public id As Long
    Public Titulo As String
End Class

A continuación leemos de una URL el webservice JSON y o recorremos para cada item del contenido


Dim request As HttpWebRequest
Dim response As HttpWebResponse = Nothing
Dim reader As StreamReader
request = DirectCast(WebRequest.Create(URL), HttpWebRequest)

response = DirectCast(request.GetResponse(), HttpWebResponse)
reader = New StreamReader(response.GetResponseStream())
Devuelve = reader.ReadToEnd()

Dim nodos() As Nodo = JsonConvert.DeserializeObject(Of Nodo())(Devuelve)

Dim count As Long = nodos.Length
For i = 0 To count - 1
     Devuelve = nodos(i).Titulo
Next

reader.Close()