Cambridgeshire Archives holds records relating to the former counties of Cambridgeshire and the Isle of Ely, as well as all archived records of Cambridgeshire County Council from 1974 onwards, and records dating from before 1974 but which cover both the old Cambridgeshire and Huntingdonshire areas. Note that historical records relating to Thorney, previously in the former county of the Isle of Ely and which is today in the Peterborough City Council area, are still held in Cambridgeshire Archives.

Only Cambridgeshire Archives has a microfiche set of the General Register Office indexes 1837-1999. 
 
Huntingdonshire Archives holds records relating to the former county of Huntingdonshire, an area largely coinciding with today's Huntingdonshire District Council, and with the Archdeaconry of Huntingdon. This area includes Alwalton, Stanground, the Ortons, and Fletton, which were historically part of Huntingdonshire but which today form part of Peterborough City Council.

Huntingdonshire Archives holds the records of Huntingdon Archdeaconry, including the Bishops Transcripts for parishes within its area. Diocesan and Archdeaconry records from the remainder of the Diocese of Ely (including BTs) are held at Cambridge University Library, and not at Cambridgeshire Archives.

Peterborough: Records relating to Peterborough can be found in a variety of places: Cambridgeshire Archives, Huntingdonshire Archives, Northamptonshire RO, or Peterborough Archives Service.

• Original parish records, probate records, Quarter Sessions records and so on for the Peterborough area north of the River Nene (the former Soke of Peterborough) are held at Northamptonshire Record Office, while those for the area south of the River Nene, previously in Huntingdonshire (Alwalton, Stanground, the Ortons, and Fletton), are held at Huntingdonshire Archives.
• Surviving records of most Peterborough schools (especially ones within the City itself), records of Peterborough Feoffees, the old city charities, and the Soke of Peterborough County Council are also held at Huntingdonshire Archives.
• Records of Peterborough Development Corporation and some other bodies are held at Peterborough Archives Service.
• Records of the County Council of Huntingdon and Peterborough are held at Cambridgeshire Archives. All historical records relating to Thorney - parish records, wills and so on - are held at  Cambridgeshire Archives as well.