Exhibit 31.2




CERTIFICATION UNDER EXCHANGE ACT RULE
13A-15 AND SECTION 302 OF THE SARBANES-OXLEY ACT OF
2002




I, Gayle Marshall
Johnson, Chief Financial Officer, certify that:




1. I have reviewed this annual
report on Form 10-K of Potomac Bancshares, Inc.;




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 annual 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)) and internal control over financial reporting as defined in Exchange
Act Rules 13(d)-15(f) and 15a-15(f) 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) Designed such internal control over
financial reporting or cause such internal control over financial reporting to
be designed under our supervision, to provide reasonable assurance regarding the
reliability of financial reporting and the preparation of financial statements
for internal purposes in accordance with generally accepted accounting
principles;




c) 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




d) Disclosed in this report any
change in the registrant’s internal control over financial reporting that
occurred during the registrant’s most recent fiscal quarter (the registrant’s
fourth fiscal quarter in the case of an annual report) 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 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
            March 30,
    2010
            
            /s/ Gayle Marshall
      JohnsonGayle Marshall Johnson, Chief Financial
      Officer




A
signed original of this written statement required by Section 302 of the
Sarbanes-Oxley Act of 2002 has been provided to Potomac Bancshares, Inc. and
will be retained and furnished to the Securities and Exchange Commission or its
staff upon request.




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