Exhibit 31-8



CERTIFICATION PURSUANT TO RULE 13a-14(a) AND 15d-14(a) OF THE SECURITIES AND EXCHANGE ACT OF 1934



I, J. Barry Mitchell, certify that:



1. I have reviewed this annual report on Form 10-K of Exelon
Generation Company, LLC;



2. Based on my knowledge, this
report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period
covered by this report;



3. Based on my knowledge, the
financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this
report;



4. The registrants other certifying
officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:



(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed
under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being
prepared;



(b) Evaluated the effectiveness of the
registrants disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and



(c) Disclosed in this report any change in the
registrants internal control over financial reporting that occurred during the registrants fourth fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrants internal control over
financial reporting; and



5. The registrants other
certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrants auditors and the audit committee of the registrants board of directors (or persons performing
the equivalent functions):



(a) All significant
deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrants ability to record, process, summarize and report financial
information; and



(b) Any fraud, whether or not
material, that involves management or other employees who have a significant role in the registrants internal control over financial reporting.



|                           |  |  |  |                          |  |                                                                                           
|-------------------------- |  |  |  | ------------------------ |  | ------------------------------------------------------------------------------------------
|                           |  | 
|Date:    February 23, 2005 |  |  |  | /s/    J. BARRY MITCHELL
|                           |  |  |  |                          |  | Senior Vice President, Treasurer and Chief Financial Officer (Principal Financial Officer)