Question: I am Having problem to make custom option dependable . I am having two custom option. In First i have 3 radio button and in second i have drop down . What i need to do is that when i select 1 radio button ,i need to display the drop down and for the rest of radio button hide that drop down. And Also one suggestion is required is that is it possible to import the dependable custom option with csv file if i use dependable custom option module(import custom option template using magmi).
Thank you

Answer: 
This cannot be done out of the box but there are a few extensions that claim to do this: 

* <http://www.magentocommerce.com/magento-connect/dependent-custom-options.html>
* <http://www.magentocommerce.com/magento-connect/dependent-custom-options-configurable.html>
* <http://www.magentocommerce.com/magento-connect/dependent-custom-options-gallery.html>
* <http://www.crunchbase.com/product/magento-dependent-custom-product-options>

They are not (all) free, but they are not expensive either. Pick the one that fits your needs (f any),
As Marius told this cannot be done out of the box. I too has recently faced the same type of requirement and i think 

* <https://store.webkul.com/Magento-Chained-Custom-Option-Template.html>

this extension fits best to my problem. I hope this will help others who are have the same problem of relating two custom options.

Cheers!! 
aton1004