Interviews in qualitative research can take three forms: structured interviews use a rigid list of closed questions; semi-structured interviews contain some pre-prepared questions as well as spontaneous follow-ups; and unstructured interviews have a theme but no preset questions beyond broad opening ones, allowing for a flexible in-depth exploration of the topic.

1. Interviewing in
Qualitative Research
Information taken from http://www.jhsph.edu/
Johns Hopkins Bloomberg School of Public Health
And from http://ro.uwe.ac.uk
Research Observatory from University of the West of England

2. structured interview
An interview with a rigid, pre-prepared list of
questions that tend to focus upon closed questions.
semi-structured interview
An interview that contains some pre-prepared
questions but that also allows the interviewer to ask
spontaneous questions to expand on the
respondent answers. Mixtures of open and closed
questions tend to be used.
unstructured interview
Also known as in-depth or non-directed interviews.
The interview has a theme or topic but no pre-set
questions, apart from the opening ones.