New Salesfoce field, populated by Marketo

[Anonymous]

Apologies. This should be so simple, but I cannot make it work.
I am collecting campaign source data via hidden fields in a Marketo form
I want to create a salesforce field so that data is also seen in salesforce, and auto-populate this field from marketo.
For whatever reason, this doesn't seem to work.
Data is in Marketo. If I create a field in Salesforce, it does not appear when attempting to map lead fields. Why?
If I give the fields the same name, will they sync automatically?

thanks

[Anonymous]

If you create a field in Marketo first and then subsequently create a field in SFDC (even with the same name), the fields will not be synched.  You have to create the field in SFDC first and make it visible to the Marketo Synch user's profile for the field to be synched with Marketo.  I believe that you can submit a request to Marketo tech support and they can map the Marketo field that you already created to the new SFDC field.

[Jep_Castelein2]

If you create a new field in SFDC and the Marketo's SFDC user account has access to it (via field-level security), the field will automatically be created in Marketo. Then collect the campaign source data into that field and not into the field that you created in Marketo.