I was facing issues regarding adding attributes to the product with color and size. (i.e configurable products). I have added products to the cart and then went to view the cart, but I didn't see the attributes color and size which should be added to the products. If product is added with attributes, onepage checkout page should display the products with attributes (size and color both).

I am posting this blog which will help us to know how to resolve this issue.

Basically cart items are listed using checkout/cart/item/default.phtml.  These are the following methods which we can use in order to show attributes to the onepage checkout.

First Method:

Now look over checkout.xml layout file and copy the whole layout <reference name="content"> node into your iwd and then start removing the template includes which you do not require.

Second Method:

Another method is using layout updates which will extend your iwd layout to checkout_cart. Which will do same thing above. You need to use <remove name=""> tag to remove extra cart includes from your iwd handle.

I have used the first method to achieve it by adding following lines of code on app/design/frontend/smartwave/porto/layout/iwd_opc.xml .

<reference name="content">
        <block type="checkout/cart" name="checkout.cart" template="checkout/cart.phtml">
            <block type="checkout/cart_coupon" name="checkout.cart.coupon" as="coupon" template="checkout/cart/coupon.phtml"/>
            <block type="checkout/cart_totals" name="checkout.cart.totals" as="totals" template="checkout/cart/totals.phtml"/>
            <block type="checkout/cart_sidebar" name="checkout.cart.sidebar" as="sidebar" template="checkout/cart/sidebar.phtml"/>
            <action method="addItemRender"><type>simple</type><block>checkout/cart_item_renderer</block><template>checkout/cart/item/default.phtml</template></action>
            <action method="addItemRender"><type>grouped</type><block>checkout/cart_item_renderer_grouped</block><template>checkout/cart/item/default.phtml</template></action>
            <action method="addItemRender"><type>configurable</type><block>checkout/cart_item_renderer_configurable</block><template>checkout/cart/item/default.phtml</template></action>
        </block>
    </reference>

Please have a look on the snapshots. This may help to analyze the situation.