Here is a list of some of the main characteristics and relative advantages/disadvantages of structured and unstructured interviews. Please insert appropriate characteristics where these have been omitted:

Short, simple, pre-worded questions
Seen as more reliable – accurate and replicable
More chance for interviewer to bias results
Interviewer needs less training
Very difficult to repeat in exactly the same way
Most appropriate for simple factual questions
Leads to greater depth of understanding
More likelihood of finding out the view of the issues held by the interviewee
Researcher therefore ‘imposes his/her own views on the research’
Most used for small number of in-depth detailed interviews
Findings easily collated and analysed
Most likely to give quantitative results