The two car crash happened at around 3pm on Wednesday, February 27 on Otley Road at the junction with Adel Willows.
A white BMW 520 and red Toyota Yaris were involved, and the 80-year-old woman was taken to Leeds General Infirmary with serious injuries.
The driver of the BMW was taken to hospital with minor injuries.
Police from the Major Collision Enquiry Team are appealing for anyone who witnessed the collision or who saw either vehicle prior to the collision to come forward. Officers are also appealing for anyone who was driving in the area at the time and has any dashcam footage to come forward.
Anyone with information is asked to contact police on 101 or use the live chat facility at www.westyorkshire.police.uk/101LiveChat quoting reference 13190106814