Be Interested In Doing vs. Be Interested To Do
Cambridge Learner’s Dictionary records interested in + -ing for wanting or considering an activity and also interested + to-infinitive in uses such as being interested to find something out. The choice is therefore meaning-sensitive rather than a simple right-versus-wrong contrast.
Both can be grammatical, but they usually do different jobs: “interested in doing” expresses interest in an activity, while “interested to learn/see/hear” often expresses attention or reaction to information.
Key details
Choose the right form
| Meaning / situation | Construction | Decision |
|---|---|---|
| interest in an activity, possibility, or undertaking | interested in + -ing | use “in” before the activity |
| attention or reaction to information in established lexical contexts | interested + to-infinitive | use with contexts such as learn, hear, see, or discover when that meaning is intended |
Quick tests
Activity-or-information test
Is the interest in doing an activity, or is the sentence expressing interest/attention in learning, hearing, seeing, or discovering information?
If yes: Use “interested in + -ing” for the activity or possibility.
If no: Use an attested “interested to + verb” context for the information/reaction reading.
Caveat: The infinitive pattern is not freely interchangeable with “interested in + -ing”; lexical context matters.
Examples
She is interested in learning another language.
“In + -ing” expresses interest in the activity.
I was interested to hear his explanation.
The infinitive expresses attention or reaction to information.
They are interested in joining the workshop.
The gerund phrase names the activity or possibility that interests them.
Further guidance
Boundary
The infinitive pattern is not freely interchangeable with interested in + -ing. Check the intended meaning and the lexical context instead of mechanically replacing one form with the other.
Construction
Use interested in + -ing for interest in an activity or possibility; use interested + to-infinitive in established contexts where the infinitive expresses what one is curious, willing, or attentive to learn, see, hear, or discover.
Decision
Both can be grammatical, but they usually do different jobs: “interested in doing” expresses interest in an activity, while “interested to learn/see/hear” often expresses attention or reaction to information.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- interested — Cambridge Learner’s Dictionary (opens in a new tab)Cambridge Dictionary · Learner-dictionary evidence distinguishing interested in + -ing from interested + to-infinitive uses.