A question was posed in one of my classes as we were talking about Unamuno this week which I would like some feedback on...if you have the time please!

The sentence was: En cuanto a la pregunta de si don Manuel es religioso, la respuesta es.... I think it should read En cuanto a la pregunta de que si don Manuel es religioso, la respuesta es....
First of all, am I correct? and secondly why? I can't seem to figure out how to explain it...yet it sounds better to me. What is making me hesitate is that during a class I took this summer, the professor spoke at length about the "dequeismo" and I am wondering if this is an example of that...a misusage ?

Gracias...

Esperanza, check out the preview of the new Diccionario Panhispánico de dudas which is being developed by all the Spanish Academies in the world. You will find information about the Dequeísmo issue there. Real Academia Española

Wrong, Esperanza:

These are very extended defects in spanish. There ins the well known "dequeísmo", consisting in saying "de que" when it shold be "que" like in "pienso de que tienes razón" (wrong).

The opposite defect is omitting "de" when needed. It is called "antidequeísmo". This is common in people who try to sound more cultured but is not. Like in "Me enteré ( de ) que su padre había muerto".

There is an easy rule: The "que" is the beginning of a "oración de relativo" (a frase beginning by "that", that's explaining something). The "oraciones de relativo" can be substitued by a word or expression. You use "de que" or "que" depending on what you'd do if you used the word or expression. Examples:

1 Me enteré de la muerte de su padre.
Me enteré de que su padre había muerto

2 Es necesaria la moderación
Es necesario que seamos moderados.

The right expression would be "de si Don Manuel...".

"de que si Don MAnuel..." doesn't sound natural at all to my ears.
"de que " should only be used when "que..." and whatever goes afterwards can be substitued by a word or expression like those in the example above.

thanks for your thoughts Antonio and Ignacio

...no hay qué...I mean, "no hay de qué." :p