Hibernate version: 3.2.5

Developed application in Hibernate. Hibernate made life simpler to connect and retrieve the data as objects.
About the problem
We have three environments dev/testing/production
While developing the application tested the hibernate performance with 50000 records and it was working fine.
When we moved to testing environment, there are around 20 million records in the database, to execute a hibernate query it is taking more than 30 min.
I would like to understand is there any issue with hibernate were it wont function properly if there are more records. Lets say 20 million records.

I can update the queries and the relationship, but before that i would like to know how hibernate perform if there are around 20 Million records

Thanks
Badri